The effects of a combined alpha- and beta-adrenoceptor blocking agent on glucose and lipid metabolism were examined in 27 out-patients with both non-insulin-dependent diabetes mellitus and hypertension. Systolic blood pressure was significantly reduced (P < 0.02), compared with the baseline value, after 1, 2, 3 and 12 months of treatment, and diastolic blood pressure was reduced after 6 and 12 months while the reductions in blood pressure at the other times were not statistically significant. Total cholesterol, and low-density and high-density lipoprotein cholesterol, decreased or showed decreasing trends during treatment, while triglycerides and very low-density lipoprotein cholesterol did not change in response to treatment. The glycosylated haemoglobin level, an indicator of glucose metabolism, did not change throughout treatment compared with its baseline value. The results suggest that a combined alpha- and beta-adrenoceptor blocking agent is less harmful to lipid metabolism and insulin sensitivity than a beta-adrenoceptor blocker would be. Such combined agents may be useful for treating hypertension accompanying diabetes mellitus.