Patient reported quality of care before vs. after the implementation of a diagnosis related groups (DRG) classification and payment system in one Swedish county. The purpose was to evaluate the effects of a diagnosis related groups (DRG)-intervention on the quality of care as perceived by patients at two surgical clinics in the County Council of Gävleborg, Sweden. The study was planned as a nonequivalent control groups design, but external factors turned it into a prospective longitudinal design. Changes in patient experiences of received care were evaluated for the period 1992-1996. Of the 40 included consecutive patients per year from each hospital, > 85% completed the questionnaire. The selection of patients was defined by diagnoses and surgical treatments, and by geographical area. The results demonstrated a decrease of the quality of care as seen from the patient perspective, especially with respect to treatment by staff. Previously stated DRG goals were partially fulfilled and the DRG-intervention was gradually implemented. Other presumed causal variables were: other reforms, restrained resources, quality assurance activities, organizational and structural changes within the county council. Further studies of the effects of health care reforms would yield more distinct conclusions, provided it would be possible to evaluate interventions prior to full-scale implementation.