This report summarises selected preliminary results from an ongoing study designed to investigate the effect of the calcium antagonist gallopamil on myocardial ischaemia during percutaneous transluminal coronary angioplasty (PTCA). To date, 12 adult males with coronary artery disease and significant proximal stenosis of the left anterior descending coronary artery (LAD) have been randomly assigned to gallopamil or placebo under double-blind conditions. Patients with recent myocardial infarction, apparent collateralisation of the LAD, myocardial failure, sinoatrial or atrioventricular block, severe hepatic disease or renal failure were excluded from the study. PTCA was performed using at least 2 balloon inflations, each of 2 minutes' duration. Gallopamil 0.4 mg or placebo (normal saline) were administered during the 10-minute interval between the 2 inflations. Blood samples were taken simultaneously from the coronary sinus and the femoral artery before and immediately after each inflation. Lactate concentration and the relative amount of activated neutrophils were selected for trend analysis. Furthermore, ECG changes were analysed by calculating the sum of the absolute ST-segment deviations (80 msec after J point, maximal T deviation) of leads I, II, III, V2, V4 and V6. In the presence of gallopamil, the degree of ST-segment/T-wave changes induced by balloon inflation was reduced. Additionally, gallopamil attenuated myocardial lactate release and appeared to prevent the increase in activated neutrophils observed during control inflations. These preliminary results suggest a beneficial effect from intracoronary administration of gallopamil during PTCA, achieved by attenuation of the ischaemic reaction during coronary occlusion.