Arnold & Siedsma

IAM Research

The Patent 1000 focuses exclusively on patent practice and has firmly established itself as the definitive 'go-to' resource for those seeking world-class legal patent expertise.

Highly-recommended - Firms: prosecution

Arnold & Siedsma has made “developing longstanding and fruitful client relationships” its overarching priority, to the delight of patrons. Based across three Belgian offices, the group recently added Hasselt-based independent patent attorney firm LC Patents to its practice – a move which brings extensive chemistry expertise to the table and should boost its profile in the life sciences, pharmaceutical and biotechnology sectors. It already enjoys an elevated reputation in the high-technology field, with Samsung a key client; the needs of the chaebol are tended to by staunch leader and well-known figure Nele D’Halleweyn and colleague Yannick Philippaerts, who together stand out for the “consistency of their guidance and their technical knowledge”. Nele has played a key role in the creation of prosecution strategies and patent portfolios all around the world, and wins plaudits for her “critical mind, courtroom skills and keen eye for detail”. Philippaerts is a seasoned patent attorney and business-minded strategist who can be relied on for all this and more – particularly by SMEs.

Gold - Firms: prosecution

Through seamless collaboration between bases in the Netherlands, Belgium, Germany and Switzerland, boutique Arnold & Siedsma provides a joined-up patent service to its illustrious clientele. For example, it is the only firm to assist Samsung across five of its business units, filing 300 European patent applications a year on behalf of the chaebol. Managing partners Joost Grootscholten and Petri van Someren run a tight ship. “Truly outstanding attorney” Grootscholten takes a measured approach and analyses a situation from all angles to come up with win-wins solutions for all parties. He specialises in software-related inventions; while van Someren has carved out a niche in the burgeoning plant breeding sector and works hand in glove with contacts around the world to secure clients cast-iron protection wherever it is needed. Alongside her in the biotechnology space is the efficient and pragmatic Marcel van Kooij, another crucial resource for start-ups and multinationals alike. The electrical, mechanical and computer engineering fields are further strongholds, thanks to the efforts of Paul Hylarides, Arjen Hooiveld and IAM Patent 1000 newcomer Bart Jacobs. “Paul’s advice is clear and honest, and provides true guidance.” A go-to for electronics briefs, he recently assisted Technical University Delft and The Boeing Company with their applications, and Fuji Seal International with patent strategy. Major league players from Japan seeking to safeguard their inventions in Europe have Hooiveld’s number on speed dial; while Jacobs has been busy managing Ampleon Netherlads’ portfolio and drafting patents for Teledyne Dalsa. “Bart is incredibly sharp, grasps complex technical concepts quickly and always does a great job. He is a pleasure to work with.” Medical technology matters are deftly handled by Rogier Brouwer and Martin Luten. Brouwer is a material science ace whose R&D know-how is underpinned by former in-house experience; while Luten “has a flexible approach and rapidly adapts to and understands foreign legal systems”. On the contentious front, Michiel Rijsdijk knocks it out of the park. An adroit coordinator of cross-border disputes, he maintains a vibrant trademark and patent practice which guarantees a holistic approach to multi-faceted proceedings.

Firm Profile

Arnold & Siedsma is an all-round service provider for the protection of intellectual property. Since 1920 your creations have been our motivation. We have 100 years of experience in the legal protection of intellectual property of inventions, trademarks and designs for individuals as well as for large multinationals, in the Netherlands and abroad. In addition to our offices in the Netherlands, Germany, Belgium and Switzerland, Arnold & Siedsma has an extensive global network of agents so that we can protect your rights anywhere in the world.

Arnold & Siedsma has more than 60 in-house technical and legal experts with knowledge of all the key innovative sectors, from biotechnology and pharmaceuticals to semiconductors and software. Each client is assigned a patent attorney who specialises in the relevant, specific discipline. Our trademark and design attorneys are the best partners for all issues related to your trademarks or protecting the unique design of your products. Our IP attorneys at law can help you with anything related to legal procedures, such as enforcing your rights.

ISO 9001 certified

For the past 100 years, we have been a reliable partner for our clients with regard to all IP issues. In 2015 we became the first large Dutch IP agency with foreign offices to be ISO 9001 certified. This certification is valid for all our offices in the Netherlands and abroad. We are proud of our ISO 9001 certification because it represents what our firm stands for: say what you do, do what you say, prove it.


At Arnold & Siedsma we believe in customised work and this can be seen in the way we operate. You can count on our personal attention, a fixed account manager and a regional office in your area.

The lines of communication with our specialists are short and personal. Service is our top priority. We stay in close touch with our clients so that we can provide you with a fast and responsive service. With offices throughout the Netherlands and Belgium, our specialists are always within proximity. At Arnold & Siedsma you will be assigned one or two dedicated account manager(s). The long-term relationship ensures that they know your business and strategy, which in turn means that they will be able to give you the correct advice for your business, in line with your multi-annual planning. Your account manager will maintain regular contact with you. The protection of your innovation is of great economic value, but can also be costly. This is why, at Arnold & Siedsma, we attach great importance to clear communication before, during and after each procedure.

Because we are a full-service provider, we have in-house specialists from all IP disciplines. Our patent attorneys, trademark and design attorneys and lawyers work closely together. We can pull together a team from several disciplines for our clients so that problems and issues are communicated between the different disciplines quickly, seamlessly and without unnecessary costs. Arnold & Siedsma is uniquely positioned as a service provider in the Netherlands thanks to this team-based approach.


Our patent attorneys have years of experience in supporting companies in various sectors and are therefore up to date with developments in your discipline. This technical knowledge and experience guarantee the optimisation of your rights. The main sectors in which Arnold & Siedsma is active are chemistry and pharmacy, electrical engineering and physics, mechanical engineering, biotechnology and food, materials and software. Our experienced specialists can assist you with the protection of your intellectual property in these sectors.

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