To evaluate the impact of patient characteristics and method of data collection on satisfaction results used for the comparison of practice locations, questionnaires were distributed to 1,208 adult outpatients at five medicine clinics, either on-site or by mail. Patient dissatisfaction with three service domains was measured: communication with the provider, courtesy of the office staff, and timeliness of care. Practice location, survey methodology, and patient characteristics were significant predictors of dissatisfaction, and adjustment for the latter two factors affected the rankings of practices by dissatisfaction rates for all three domains. Further study of the impact of patient characteristics and method of data collection should be conducted before the comparison of unadjusted satisfaction results becomes the accepted standard.