Progress testing in the Netherlands was originally developed at Maastricht University. Since the late 1990s, a collaboration has started between three medical schools to jointly produce and administer the progress test. Currently, the progress test is administered to five out of eight medical schools in the Netherlands. The collaboration has led to substantial decrease in necessary resources per participating school. Also, the data provide a rich source for comparisons between schools and can be instrumental in inducing improvements to the curricula. Logistics of large-scale administrations and possible differences of views on item quality could be seen as a disadvantage. Also, it is not always easy to fit the test in the local regulatory structure, because it is only partly owned by each individual school. Important lessons for us have been that the advantages of the collaboration clearly outweigh the disadvantages. Of course, good collegial communication is needed, but this is not enough: a legal binding agreement has to be drawn up. Most importantly, such a collaboration creates a critical mass to enable multi-centre research and development projects on progress testing.