OBJECTIVE: We investigated the effects of bisoprolol and losartan on subjects with essential hypertension, by conducting heart rate variability (HRV) analysis of ECG signals. Our intention was to establish the set of linear and nonlinear heart rate variability parameters, which could be used as a noninvasive markers in the treatment of hypertension. MATERIALS AND METHODS: Sixty subjects with essential hypertension included in this study were divided in two groups. During the four weeks medical treatment, the first group was administered with daily oral dose of 5 mg of bisoprolol and the second with daily oral dose of 50 mg of losartan. We recorded ECG signals, and performed HRV analysis of consecutive RR time intervals, before and after a month of pharmacological therapy. RESULTS: IN THE CASE OF BISOPROLOL, STATISTICALLY THE MOST SIGNIFICANT CHANGES OF HRV PARAMETERS WERE: TP (1814.1 +/- 1731.3 ms(2) vs. 761.3 +/- 725.0 ms(2), P < 0.0001), RR (870.2 +/- 105.7 ms vs. 1027.2 +/- 150.0 ms, P < 0.0001), HR (70.81 +/- 8.42 bp/min vs. 60.10 +/- 9.52 bp/min, P < 0.0001). In the case of losartan, the most significant changes were: SDNN (43.16 +/- 17.27 ms vs. 237.98 +/- 118.54 ms, P = 0.002), rmSDD (27.09 +/- 18.27 ms vs. 46.82 +/- 37.71 ms, P = 0.003), SD2 (55.18 +/- 20.6 vs. 70.67 +/- 26.12, P < 0.019) and DF2 (0.69 +/- 0.21 vs. 0.86 +/- 0.25, P < 0.014). CONCLUSION: Effects of bisoprolol and losartan were especially manifested among the set of linear HRV parameters. As a consequence of effect of losartan, we singled out the nonlinear parameters SD2 and DF2.