1. We studied the effect on plasma lipids of sotalol given orally over a 12 month period to patients with essentially hypertension. 2. Plasma free fatty acid concentration was lower than initially at 1, 3, 6 and 12 months. The difference was significant (P less than 0.01) at 1 and 3 months. 3. Plasma cholesterol (VLDL + LDL-cholesterol) increased during treatment. Plasma total cholesterol increased from 5.49 +/- SD 0.94 mmol/l at the beginning to 6.37 +/- 1.10 mmol/l at 12 months (P less than 0.01). 4. HDL-cholesterol concentration and the ratio of HDL-cholesterol to total cholesterol decreased significantly. The ratios were 0.28 and 0.18 at the beginning and at 12 months respectively (P less than 0.001). 5. Plasma triglycerides increased simultaneously from 1.14 +/- 0.31 to 1.89 +/- 0.99 mmol/l (P less than 0.01).