We studied the effects of tiapamil during myocardial infarction in the anaesthetized baboon. 10 animals received placebo and 8 animals the drug. After basal measurements the left anterior descending coronary artery was ligated. Measurements were repeated at 15min and 2-hourly until the 12th h after occlusion. Placebo or drug (1 mg·kg<sup>-1</sup> and 50 µg·kg<sup>-1</sup> •min<sup>-1</sup>) was administered 20 min after occlusion. Tiapamil decreased afterload by reducing peripheral resistance. Blood flow to the peripheral ischaemic zone was increased. These effects resulted in myocardial salvage manifest as a reduction in serum creatine kinase (MB) isoenzyme levels and less myocardial damage at 12 h than that predicted for the placebo group by S-T segment mapping 15 min after occlusion.