BACKGROUND: In general, there is a need for testing new interventions in large randomized controlled trials. Depending on the research question it may be advantageous to establish multicenter studies as a way of organizing clinical trials in order to increase study power. MAIN OBJECTIVES: The object of this study was to investigate the development in the organization of multicenter studies, the distribution of studies within different clinical specialties, across continents, and investigate the differences related to testing various interventions. METHODS AND MATERIALS: A literature search was done in MEDLINE for multicenter studies published in 1995, 2000, 2005, and 2010, respectively. Data extraction identified data related to clinical specialties, interventions, participating patients, departments, countries, and continents. RESULTS: The number of multicenter studies increased from 112 in 1995 to 1,273 in 2010, with a larger share of multicenter studies being performed in Europe and North America. The pharmacological interventions were primarily being tested in medical studies followed by the device tests predominantly in surgical studies. The number of included patients as well as the number of participating departments increased during the time span, though the increase in studies was most evident in Europe and North America compared with the rest of the world.