Twenty six hypertensive patients and 25 control subjects were studied and their systolic time intervals (STI) were measured. It was found that an alteration in STI, signifying left ventricular dysfunction sets in most of the hypertensives earlier than any evidence of left ventricular hypertrophy (LVH) by clinical, radiological or electrocardiographic criteria. The parameters affected are the PEP interval which shows prolongation and PEP/LVET ratio which is increased. After treatment the left ventricular performance was found to improve in those who did not reveal evidence of LVH. Thus STI may be a sensitive indicator of early left ventricular dysfunction in hypertensives and a useful guide to assess improvement after treatment at a stage when other non-invasive methods are not so useful.