Seven selective left ventricular angiocardiograms that permitted measurement of end-diastolic volume for 5 consecutive cardiac cycles were analyzed.Neither end-diastolic volume nor end-systolic volume changed significantly between the first and second cycles after ventricular opacification. A progressive increase in the major and minor ventricular semiaxes occurred beginning with the third opacified cycle. Correspondingly, the average end-diastolic volume and end-systolic volume increased by 6.9 ml and 3.4 ml, respectively, between the second and third cardiac cycles. Ventricular volumes progressively increased between the third and fifth cardiac cycles in each patient.These data suggest that sodium diatrizoate has a negative inotropic effect on left ventricular myocardium by the third cardiac cycle after injection. Physiologic information from cineangiocardiography should be derived from the first 2 cardiac cycles after opacification.