Abstract
Hyponatraemia was observed in 11 out of 14 consecutive patients with acute myeloid leukaemia and its variants. Metabolic studies on these patients revealed an early increase in the urinary sodium excretion, negative free water clearance, and urine osmolality inappropriately higher than that of the serum. It is postulated that this syndrome is caused by a substance released from the primitive cells of the abnormal myeloid series.