Monotherapy with caposide-50 (C-50) was compared to combined therapy C-50 + melatonin in 22 patients with essential hypertension stage II (mean age 60 years). The patients were divided into two groups. Group 1 received C-50 at 8.00 a.m., group 2 received C-50 at 8.00 a.m. and melatonin at 10.00 p.m. in a dose 3 mg. Before the treatment and 14 days after it echo-CG was made to assess hemodynamics. Also, 24-h monitoring of arterial pressure was performed. The findings were analysed with variance statistics and cosinor-analysis. Group 1 achieved a moderate hypotensive effect. Circadian rhythm of systolic blood pressure was abnormal. Group 2 patients achieved more pronounced decline of systolic, diastolic and mean arterial pressures. Circadian rhythm of these pressure did not return to normal.