One hundred fifty-four males attending an outpatient diabetes clinic were interviewed to determine the incidence of alcohol use among them and to identify mechanisms by which alcohol use adversely affects the control of diabetes. Specifically, we determined how diabetic patients' use of alcohol is related to compliance with their diabetes treatment regimen, and diabetic patients' expectations of benefits from drinking alcohol and actual alcohol use is related to their quality of life. Greater alcohol use was related to poorer prescribed insulin injection compliance (p < 0.01), and stronger expectations of immediate, positive consequences of drinking alcohol were related to several indices of lower quality of life (p < 0.005). These results imply interactive relationships among diabetics' alcohol use and expectancies, treatment compliance, and quality of life.