The rate at which medical patients physician-referred to an 8-week stress reduction program completed the prescribed intervention was measured and predictors of compliance sought. Seven hundred eighty-four consecutive patients who enrolled in the program over a 2-year period were studied. Of these, 598 (76%) completed the program and 186 (24%) did not. Multiple regression analysis showed that (1) among chronic pain patients, only sex discriminated between completers and noncompleters, with females more than twice as likely to complete the program as males (odds ratio = 2.4; 95% CI = 1.2, 4.4); (2) among patients with stress-related disorders, only the OC scores of the SCL-90-R discriminated between completers and noncompleters (odds ratio = 2.0; 95% CI = 1.2, 3.4). Completion rates for specific diagnoses are reported and discussed. The high rate of completion observed for this intensive program in health behavior change is discussed in terms of the design features and therapeutic modalities of the intervention.