Forty consecutive patients with coronary artery disease undergoing left ventricular angiography took part in a randomised double blind trial comparing a conventional contrast medium sodium meglumine iothalamate (Cardio-Conray) with the low osmolar agent iopamidol. Iopamidol produced a smaller rise in heart rate and a smaller fall in left ventricular systolic pressure, but the changes in left ventricular and diastolic pressure and maximum rate of change of pressure (dP/dt max) were not different. The numbers of extrasystoles per minute for five minutes after ventriculography were similar in both groups except for the first 15 seconds, when the number of extrasystoles was increased in the iopamidol group. The frequency and magnitude of symptoms (heat, angina, headache, nausea) were significantly different in two groups. Iopamidol caused less haemodynamic disturbance than Cardio-Conray, although the improvement is small and offers no advantage in reducing symptoms or extrasystoles.