We compare health maintenance organization enrollees' evaluations of the care they received from family physicians and chiropractors for low back pain. Patients of chiropractors were three times as likely as patients of family physicians to report that they were very satisfied with the care they received for low back pain (66% versus 22%, respectively). Compared with patients of family physicians, patients of chiropractors were much more likely to have been satisfied with the amount of information they were given, to have perceived that their provider was concerned about them, and to have felt that their provider was comfortable and confident dealing with their problem. Although the more positive evaluations of chiropractors may be related to differences in the patient populations served by the two providers or to benefits of spinal manipulation, it is suggested that a potentially more potent force--the therapeutic effect of the patient and provider interaction itself--may explain the observed differences.