The effects of chlorthalidone (mean dose 25 mg/day), metoprolol (mean dose 200 mg/day) or their combination (logroton) on blood pressure, lipids, lipoproteins and circulating atrial natriuretic factor (ANF) were evaluated in a controlled trial of 42-week duration in 33 hypertensive patients. There was a significant reduction in mean arterial pressure after chlorthalidone and metoprolol treatments. This effect was more pronounced with the chlorthalidone/metoprolol combination (logroton). There were no significant changes in mean ANF levels after any drug regimen, although a tendency to increase was observed after six weeks of treatment with metoprolol. Both chlorthalidone and metoprolol as monotherapy increased the total triglycerides. This effect was less pronounced with logroton. During metoprolol treatment, HDL cholesterol decreased significantly, whereas VLDL-C increased. When combined drug therapy was administered, the unfavorable effects on HDL-C were partially blunted and VLDL-C returned to baseline. LDL-cholesterol did not change significantly during any drug regimen nor did the ratio of LDL-C/HDL-C. Logroton significantly increased the VLDL apo B levels in patients who had received chlorthalidone as monotherapy but had no effect in patients already treated with metoprolol. Neither treatment had a significant influence on the ratio of LDL-C/B. There were no serious adverse events reported throughout the study. It is concluded that logroton may be an effective combination therapy that produces less adverse effects on lipid and lipoprotein metabolism than chlorthalidone or metoprolol monotherapies.