The effects of plasma lipids, blood glucose, and serum total cholesterol, LDL-cholesterol, VLDL-cholesterol, 6-month period were studied in 18 patients with essential hypertension. There were no significant changes in the concentration of serum total cholesterol. LDL-cholesterol, VLDL-cholesterol, and triglycerides during treatment periods with pindolol or atenolol, although there was a tendency to higher triglyceride levels during atenolol treatment. The serum HDL-cholesterol levels were significantly lower after 6 months of therapy with atenolol than before treatment, but HDL-cholesterol levels increased slightly during pindolol treatment. The ratio of HDL-cholesterol to total cholesterol decreased significantly during 6 months of treatment with atenolol. Fasting blood glucose concentrations did not change significantly during 6 months of treatment with pindolol or atenolol, but during oral glucose tolerance test, blood glucose values at 60 min were raised after pindolol therapy. Serum insulin levels during oral glucose tolerance test at 120 min were decreased after pindolol therapy, but no significant changes were found in C-peptide levels during treatment periods.