We studied dialysis-associated arrhythmia in 48 uraemic patients < 35 years on chronic haemodialysis (HD) (> 3 months). Holter findings showed only minor arrhythmia; atrial in 42% of patients and ventricular in 38%. ST-segment depression > 1 mm was observed in 58% of patients; 80% had arrhythmia, and 36% experienced anginal pain. HD caused a significant increase in QTc, QTdc and Ca2+ level, while K+ level was significantly decreased. Patients who experienced arrhythmia during HD had higher left ventricular mass and left ventricular mass index, lower post-dialysis K+ level, higher QTc and QTdc both before and after HD. They were more frequently hypertensive. ST-segment depression was significantly related to ventricular arrhythmia.