Data of 44 patients with congenital complete heart block and structurally normal heart have been analysed. Thirty one patients were asymptomatic (group I) and 13 patients had symptoms of low cerebral perfusion like syncope, near syncope or convulsions (group II). A ventricular rate on surface ECG was found to be significantly lower in the symptomatic group (56.7 +/- 13.2 beats per minute, bpm, in group I and 46.5 +/- 6.0 bpm in group II). Similarly wide QRS escape rhythm of greater than 0.10 seconds was more often seen in group II (2/13) as compared to group I (2/31) though the difference did not reach statistical significance. Presence of pauses of more than 3.0 seconds on ambulatory ECG monitoring were infrequent in both the groups (group I 1/7, group II 2/7), however more often seen in group II. Electrophysiological studies carried out in 11 patients were not helpful in differentiating the two groups and all the patients including two with a wide QRS escape rhythm on surface ECG showed suprahisian level of block. The corrected junctional recovery time in two groups did not show any statistical difference. A persistently slow ventricular rate of less than 50 bpm during waking hours, wide QRS escape rhythm and pauses of greater than 3 seconds on ambulatory monitoring are suggestive of high risk to the patient and may justify implantation of permanent pacemaker even in asymptomatic patients.