OBJECTIVE The aim of the study was to examine the extent of use of acute psychiatric inpatient care, and to determine sociodemographic and disease-related characteristics of so called "heavy users". METHODS A cohort of 1811 patients with first hospitalisation in 1995 was followed by means of the German psychiatric basic documentation (DGPPN-BADO) over a five-year period from 1995 to 1999. RESULTS The average cumulative length of stay was 63.2 days (SD 98.4), the median 32 days. 5 % of patients stayed in hospital more than 238 days and 1 % even more than 538.1 days within five years. 50 % of patients "consumed" only 10 % of inpatient days, whereas other 10 % of patients accounted for nearly 50 % of the resources. By means of a regression analysis ten significant predictors for a long cumulative hospital stay could be found, e. g. schizophrenia, personality disorder, socio-therapeutic modalities, sheltered living, and low psychosocial capability (GAF) at discharge. Within five years an average number of hospital stays of 1.8 (SD 2.1) was found. 5 % of patients had more than four inpatient stays, 1 % even more than ten. Regressions analysis revealed seven significant predictors for a high number of hospital stays, e. g. alcohol dependence, comorbid alcohol abuse, and a short interval between first and second admission. CONCLUSIONS As no distinct group of "heavy user" could be identified, individual treatment strategies should be addressed, and qualitative studies and in-depth statistic analyses must be performed.