This paper identifies the social changes and developments in public mental health that have contributed to fluctuations in the use of emergency compulsory admissions in Rotterdam, the Netherlands. Annual reports and administrative data over the years 1929-2005 indicate the impact of general and local factors. Demographic changes and statutory regulations were important general factors, but do not explain particular swings in the number of compulsory admissions. Key local factors were: the availability of alternative arrangements such as emergency centres and sheltered homes; an interpretation of the criteria for compulsory admissions shared by all disciplines involved; and better collaboration between services. These factors suggest that if the increasing use of compulsory admissions is to be reversed, a coordinated effort is needed.