The electrical pattern of the vas deferens, or electrovasogram (EVG), was studied in 22 healthy volunteers, 20 vasectomy subjects and 18 individuals after vasectomy reversal. Their mean ages were 38.8 +/- 7.3, 44.3 +/- 7.9 and 58.6 +/- 6.6 years, respectively. Two electrodes were applied to the posterior aspect of the upper part of the scrotum. During the operation of vasectomy reversal, an electrode was applied directly to each of the two vasal segments before and immediately after vasovasostomy. The electrical activity and intravasal pressure were measured. In normal subjects, slow waves or pacesetter potentials (PP) were recorded. They had identical frequency and a regular rhythm from the two electrodes and were consistent in the individual subject on all test days. PP were followed randomly by bursts of action potentials (AP). In vasectomized subjects, PP from the proximal vasal segment exhibited an irregular rhythm (vasoarrhythmia). During operation for vasectomy reversal, the proximal vasal segment recorded vasoarrhythmia whereas the distal segment revealed a silent EVG. Intravasal pressure was normal (p > 0.05) in the distal segment but high (p < 0.05) in the proximal segment. EVG performed 1-6 years after vasectomy reversal showed a normal pattern in four subjects and diminished frequency and amplitude in three. These seven subjects had impregnated their wives and had an obstructive interval of < 3 years. The 11 subjects who did not produce a pregnancy had a vasoarrhythmic EVG and an obstructive interval of > 3 years. In conclusion, an EVG could be identified for normal subjects. Vasectomy resulted in a vasoarrhythmic EVG pattern which proved to be correctable by vasectomy reversal if the obstructive interval was short.