Retrospective examination of weekly electrocardiograms of 13 patients on zero calorie intake for 97 +/- 25.4 d (mean +/- standard deviation) for morbid obesity demonstrated a significant progressive reduction in QRS voltage by the seventh week. There was a significant prolongation of the QTc interval in the group during the eighth week and in seven patients the QTc had lengthened beyond normal by the end of the fast. The importance of these changes is illustrated by one patient with QTc prolongation who sustained two cardiac arrests due to torsade de pointes. We recommend regular in-patient electrocardiographic monitoring for obese patients on therapeutic starvation.