Abstract:Physical medicine, which in the context of this article includes mechanotherapy, hydrotherapy, balneotherapy, electrotherapy, light therapy, air therapy, and thermotherapy, became a new field of labor in the healthcare domain in the Netherlands around 1900. This article gives an account of the introduction and development of mechanotherapy as a professional activity in the Netherlands in the 19 th century. Mechanotherapy, which historically included exercises, manipulations, and massage, was introduced in this country around 1840 and became one of the core elements of physical medicine towards the end of that century. In contrast to what one might expect, mostly physical education teachers, referred to as "heilgymnasts," dedicated themselves to this kind of treatment, whereas only a few physicians were active in this field until the 1880s. When, in the last quarter of the 19 th century, differentiation and specialization within the medical profession took place, physicians specializing in physical medicine and orthopaedics began to claim the field of mechanotherapy exclusively for themselves. This led to tensions between them and the group of heilgymnasts that had already been active in this field for decades. The focus of attention in this article is on interprofessional relationships, on the roles played by the different professional organizations in the fields of physical education and medicine, the local and national governments, and the judicial system, and on the social, political, and cultural circumstances under which developments in the field of mechanotherapy took place. The article concludes with the hypothesis that the intra-and inter-occupational rivalries discussed have had a negative impact on the academic development of physical medicine, orthopaedics, and heilgymnastics/physical therapy in the Netherlands in the first half of the 20 th century.