In 71 patients, divided into four groups by the type of supraventricular tachycardia (SVT) during electrophysiological examination, 918 stimulations were implemented by the method of rapid continuous stimulation of the atria (overdrive) in order to interfere with a SVT paroxysm. In addition to characteristics of tachycardia the authors evaluated parameters of overdrive stimulation, i.e. the duration of the stimulation cycle (CL STIM), the ratio CL STIM/CL SVT, the number of stimuli required to terminate tachycardia (N STIM) and their mutual relations. In the group of atrioventricular reciprocal tachycardias (WPW, n = 17) the effectiveness was 50.4%, CL SVT 334 +/- 43 ms, the ratio CL STIM/CL SVT 78.3 +/- 12%, the median of N STIM 14 +/- 6. In the group of AV nodal tachycardias (AVNR, n = 26) the effectiveness is 53.1%, CL SVT 356 +/- 70 ms, CL STIM/CL SVT 77 +/- 8.6%. In the group of atrial tachycardias (AT, n = 5) the effectiveness was 62.3%, CL SVT 348 +/- 24 ms, CL STIM/CL SVT 73.7 +/- 7.5%, N STIM 6 +/- 4. In the group of atrial flutter (AFL, n = 23) the effectiveness was 9.2%, CL SVT 226 +/- 29 ms, CL STIM/CL SVT 84.5 +/- 8.2%, N STIM 22.5 +/- 9. The effectiveness of overdrive stimulation in AFL is significantly lower than in other groups of SVT. The regression correlation in the entire group of tachycardias for calculation of a suitable duration of CL STIM--0.855 x CL SVT--28 (ms), the median number of stimuli N STIM 14 +/- 7.(ABSTRACT TRUNCATED AT 250 WORDS)