The ability of CGRP to increase blood flow in the coronary circulation of the anaesthetized pig was studied in a constant pressure perfusion model. Human alpha-CGRP, when infused close-arterially into the left anterior descending coronary artery perfused at constant pressure, produced a marked and prolonged dose-related increase in coronary flow, at doses above 10 pmol min-1. The gradient of the flow/pressure curves at each dose increased with an increase in pressure, indicating a drop in the resistance of the coronary bed. No significant change was observed in heart rate, left ventricle pressure, mean arterial pressure or cardiac output.