The aim of this study was to assess changes in attitudes and behaviour related to efficiency and quality of care after introduction of performance-based reimbursement. The study consisted of two parts. Part One was performed in 1992-94 as a repeated cross-sectional study of physicians in Stockholm County Council working with a newly introduced performance-based reimbursement system. Part Two was a similar study conducted in 1994 in 11 Swedish councils without performance-based reimbursement. The results show a significant difference between the two groups of physicians in attitudes concerning changes in quality of care and premature discharge from hospital. Despite concern about quality and premature discharge, physicians in Stockholm were found to have changed their behaviour in that the average length of stay in 1994 was about one day shorter in Stockholm than in the other 11 county councils. This indicates that the performance-based reimbursement system may strengthen the incentive to increase efficiency.