The aim of this study was to assess the diagnostic possibilities of recording of time-domain parameters of atrial signal-averaged electrocardiogram (ASAECG) in patients with electrically-induced paroxysmal atrial fibrillation (PAF). The investigation was done in 53 patients (34 male and 19 female) mean age 47.6 +/- 13.1 with electrically induced sustained PAF- > 30 sec (group I). As a controls were forty patients (28 male and 12 female) mean age 46.2 +/- 15.3 (group II). The following time-domain parameters of ASAECG were calculated: the root mean square voltage of the terminal 10,20,30 ms of the filtered P-wave (RMS10,20,30) and total duration of filtered P-wave (PWD) and also time duration of P-wave from Frank's leads X,Y,Z (XP,YP,ZP). The values of RMS10,20,30 were statistically significant lower in patients with PAF than in controls, respectively RMS10: 3.9 +/- 1.4 microV vs 5.4 +/- 2.3 microV, p < 0.005, RMS20: 5.3 +/- 2 microV vs 6.8 +/- 2.2 microV, p < 0.001 and RMS30: 6.8 +/- 2.1 microV vs 7.4 +/- 3.6 microV, p < 0.05. Also the values of PWD were significantly longer in group I: 121 +/- 14.6 ms than in group II: 113.9 +/- 13.5 ms, 1 p < 0.02. Analysing the values of XP,YP,ZP it's occurred that only YP in PAF patients was statistically longer than in control, respectively 111 +/- 14.8 ms vs 96.7 +/- 13.8 ms, p < 0.001. The best differential criteria for identification of patients with electrically-induced PAF were RMS20 < 6 microV and PWD > 118 ms and gave sensitivity of 52%, specificity of 79%, positive predictive value of 68%, negative of 66% and diagnostic accuracy of 67%. CONCLUSIONS 1. In patients with electrically-induced PAF the lower values of RMS10,20,30 and longer PWD were detected. 2. The criteria for identification of patients with electrically-induced paroxysmal atrial fibrillation were the values of RMS20 < 6 microV and PWD > 118 ms.