1. Intravenous infusions of lipid-free albumin were used to lower the arterial non-esterified fatty acids (NEFA)/albumin ratio during coronary occlusion in dogs.
2. Reduction of the NEFA/albumin ratio was accompanied by proportionate reductions in myocardial uptake of NEFA and the degree of ST segment elevation in epicardial electrocardiographic recordings from the ischaemic zone. Aortic pressure and heart rate were unchanged.
3. Infusions of control albumin preparations had no effect on the NEFA/albumin ratio or ST segment elevation.
4. These observations support the proposition that the disturbance of cellular function during myocardial ischaemia is influenced by the degree of saturation of albumin-binding sites with NEFA and by their availability.