The adequacy of retrograde delivery of cardioplegic solution to the right ventricle ist controversial. To evaluate this issue, we excised the plegic heart in 11 bovine experiments and infused an India ink solution (10 ml of India ink in 300 ml NaCl 0.9%) into the coronary sinus (n = 7) at a pressure of 60 cm H2O and into the aortic root (n = 4) at a pressure of 120 cm H2O. After fixation, the ventricles were cut in 11 transversal slices. The portion of coloured (= perfused) ventricular myocardium was calculated with computer-aided morphometric analysis. With antegrade infusion, 95 +/- 5% (mean +/- standard deviation) of the left ventricular volume (left ventricular free wall plus interventricular septum) was stained, with retrograde infusion 94 +/- 3%. Perfusion of the right ventricle was significantly lower with retrograde infusion (antegrade infusion 93 +/- 8%, retrograde 45 +/- 13%, p < 0.001), especially in the basal segments (basal vs. apical: 16 +/- 26% vs. 82 +/- 5%, p < 0.001). The adequate delivery of retrograde infusion to the left ventricle and septum allows good left ventricular myocardial protection with retrograde cardioplegia. Because the retrograde delivery to the right ventricle is markedly inadequate and nonuniform, the quality of right ventricular protection with retrograde cardioplegia has to be questioned.