History
The history of Arnold & Siedsma runs more or less parallel with the legal developments in the field of patents and trademark and design rights. National and international economic developments also played a part in the company’s growth and market strategy.
The history of Arnold & Siedsma runs more or less parallel with the legal developments in the field of patents and trademark and design rights. National and international economic developments also played a part in the company’s growth and market strategy.
A trip down memory lane
Until 1900, it was not possible to file a patent in the Netherlands as an ‘exclusive right for the creation and sale of an item or for the exploitation of an invention’. Patent applications from Dutch companies could therefore only be filed abroad. The Dutch Patent Act (1910), which resulted in the establishment of the Dutch Patent Office in 1912, put an end to this undesirable situation. Since then, the Netherlands have had a modern legal and technical system for patents from the inventions of Dutch and foreign companies.
The establishment of the Patent Office in 1912 heralded the growth in the number of Dutch patent attorneys submitting and defending patent applications on behalf of companies. In response to the increasing competition between individual patent attorneys, some patent attorneys chose to work together.
The founders of Arnold & Siedsma
The founders of the present-day Arnold & Siedsma were the mechanical engineers A.E. Jurriaanse and J. Knoop Pathuis. In 1920, they joined forces and made the strategic decision to base themselves in The Hague, the city in which the Patent Office was also located.
The first half of the company name came from electrical engineer A.F. Arnold, who joined the company in 1934. Through his contribution, electrical engineering soon became a company department in its own right. The same thing happened with the department dealing with chemical patents, which were being handled in increasing numbers in that period.
In 1964, mechanical engineer A. Siedsma became a director of the company.
In 1974, it was decided that the company should no longer be named using the surnames of new partners. The Arnold & Siedsma patent office was established.
Significant developments
The Arnold & Siedsma order portfolio enjoyed strong growth during the depression of the 1930s. In times of economic difficulties, the number of patents actually increases rather than decreases.
Although this growth stalled temporarily during the Second World War, it took off again after 1945. This was partly due to the increased internationalisation of intellectual property rights.
Other developments also influenced the growth of Arnold & Siedsma. For example, the ‘Uniform Benelux Law on Trademarks’ was introduced in 1971. As a result of this law, all trademarks used in the Netherlands, Belgium or Luxembourg then had to be registered with the Benelux Trademark Office in order to maintain the associated rights. It formed the basis for a separate Arnold & Siedsma trademark and design department.
Increasing the number of offices
Apart from increasing the number of disciplines, from the 1970s onwards Arnold & Siedsma focused on increasing the number of offices. The ambition was, and is, to operate close to the offices of clients. This resulted in the opening of an office in Enschede in 1973 and an office in Breda in 1975, which will close in November 2026. Leeuwarden followed in 1982, Utrecht in 1990, Nijmegen in 2000, Eindhoven in 2010 and Brussels in 2012. In July 2020, an office in Hasselt was added.
In mid-1970, multinationals from countries such as the United States and Japan began to approach Arnold & Siedsma to file patents. To provide a good service to multinationals, Arnold & Siedsma set up global networks with its colleagues abroad.
In 1977, Arnold & Siedsma also opened up a branch office in Munich, as the headquarters of the European Patent Office were located there. This office in Munich is also well placed to attend informal interviews and oral proceedings.
There was also a good reason for opening an office in Antwerp in 1987 after a new patent law was passed in that year. This law made it possible for us to register our Dutch patent attorneys in Belgium also. Our Belgian office then merged with the Ottelohe office in Antwerp in 1998. In 2022, Arnold & Siedsma merged with the Belgian IP firm LC Patents. This strengthened our position in Belgium and expanded our expertise in pharmaceuticals, life sciences and biotechnology.
Arnold & Siedsma expanded its activities in 1993 by adding a legal department, which later merged with Amsterdam-based law firm Steinhauser Rijsdijk in 2010. This also gave the firm an office in Amsterdam. The advantage of having a legal department is that, besides establishing intellectual property rights for its clients, Arnold & Siedsma can personally defend them in legal proceedings.
Expansion, internationalisation, mergers and the addition of new disciplines have more than doubled the size of the firm and broadened our client base. Opposition work at the European Patent Office has grown sharply as well: with more than 300 hearings since 2020, Arnold & Siedsma is one of the most experienced firms in Europe in this field.
Joining the Rouse Group
In September 2025, after more than a century as an independent firm, Arnold & Siedsma merged with Rouse, an international IP services group. The combination brings our European patent, trademark and litigation practice together with Rouse’s network across Asia, Africa, the Middle East and Europe.
For clients, the day-to-day work stays familiar: the same teams, the same contacts, the same name. What changes is reach. Clients can now be supported across a far wider set of jurisdictions from within one group, and both organisations can invest together in technology, data and shared platforms.
