summary 
background In the Netherlands little research has been done on the regional variability in the implementation of the law on Special Admissions to Psychiatric Hospitals (Dutch acronym Bopz).
aim To investigate regional variability in the numbers, combinations and characteristics of emergency compulsory admissions and other types of legally authorised admissions.
method Data from the Bopz information system covering a 12-month period were analysed. Missing data were supplied by the courts in Maastricht, Groningen and Rotterdam.
results There was regional variability in the way in which compulsory measures were implemented, particularly as far as emergency compulsory admissions were concerned. The relative number of Bopz measures increased in relation to the degree of urbanisation. Rotterdam had the highest percentage of emergency compulsory admissions. Patients in Maastricht and Rotterdam were more often involved in legally authorised admissions only. In Rotterdam an unlinked combination of emergency compulsory admissions and legally authorised admissions was more common. In Maastricht a larger number of patients were admitted because they were a danger to themselves, whereas in Groningen and Rotterdam admissions were also used as a means of safeguarding the public.
conclusion The number of admissions and the diversity of Bopz measures are highest in urban areas. Regional variations in the way in which compulsory measures are applied persist, but there is room for improvement in the monitoring of the effects of these differences and the types of services that are available.