1. Nineteen healthy men aged 50 years, with untreated, mild essential hypertension WHO group I, were randomized into two groups to study the effect of treatment (18 weeks) with oxprenolol (n = 10) and atenolol (n = 9) on serum cholesterol fractions, total triglycerides and uric acid.
2. Oxprenolol lowered high density lipoprotein (HDL) cholesterol by 11.4% (P < 0.02) and cholesterol ratio (HDL cholesterol × 100/LDL + VLDL cholesterol) by 13.7% (P < 0.05). Atenolol lowered HDL cholesterol by 16.5% (P < 0.02) and cholesterol ratio by 19.2% (P < 0.01).
3. Oxprenolol and atenolol raised total triglycerides by 20.0% and 17.9% respectively. Only with atenolol was this increment statistically significant (P < 0.05).
4. The HDL cholesterol lowering effect of oxprenolol and atenolol observed in the present study may have clinical importance, since such metabolic side effects have been postulated to counteract the beneficial effect of blood pressure reduction on development of atherosclerosis and coronary heart disease in mild essential hypertension.