Levels of serum lipids, uric acid and body weight are reported from a controlled trial of drug treatment of middle-aged men with uncomplicated mild hypertension. The results come from 300 men after three years of follow up; 150 men in the treatment group and 150 men in the control group. The treatment has been standardized starting with hydrochlorothiazide alone and adding alpha methyldopa when necessary. In case of side effects, alpha methyldopa was replaced with propranolol. Pretreatment results demonstrated a strong covariation among body weight, uric acid and triglycerides. In the entire treatment group, there was no significant change in triglycerides after three years (increase from 1.85 to 2.02 mM/liter, P greater than 0.05). Cholesterol was also unchanged. Further analysis showed that certain patients reacted with an increase in triglycerides during treatment: those prone to a distinct increase in uric acid and those gaining weight. Those who needed combination therapy (having the highest pretreatment blood pressure) showed most of the increase in triglyceride and uric acid. In the group treated with hydrochlorothiazide alone, the triglycerides were unchanged. However, those selected from this group with a distinct increase in uric acid also showed an increase in triglycerides. The treatment increased the pretreatment positive correlation between uric acid and triglycerides.