The purpose of this study was to analyse the influence of the hospital size, measured as the number of annual patient enrolments in the Finnish Leukaemia Group trials in the period 1979-85, on response rate and survival after conventional chemotherapy for multiple myeloma. The 432 myeloma patients for this study were derived from 4 prospective multicentre trials of the Finnish Leukaemia Group. The comparisons of the response rate to primary chemotherapy, progression-free survival time (PFS), response rate after first relapse and overall survival time (OS) were made between patients treated in 3 hospital categories according to annual enrolment rate. 273 of the patients had been treated in "large" hospitals, 120 in "intermediate" and 38 in "small" ones. The median OS of patients aged up to 70 yr was 49 months and that of patients older than 70 yr was 31 months. There were no significant differences in response rate, PFS, response rate after first relapse and OS between the hospital categories. The most important endpoints in the treatment of multiple myeloma, response rate, PFS and OS are independent of the size of the hospital, measured as the number of annual patient entries in the trial. This allows the decentralisation of the conventional chemotherapy of multiple myeloma, within the framework of properly organised clinical trials.