The effect of phosvitin (1 g kg(-1), i.p.) on ecg changes induced in rats by a reduction of partial oxygen pressure in the respiratory mixture was studied. Phosphocreatine, phosphoserine, ATP and Na2HPO42H2O were also administered intraperitoneally for comparison. Phosvitin alone was found to prevent the hypoxia-induced T-wave changes (flattening or disappearance), which were also temporarily aggravated by injection of noradrenaline. As to the metabolic, hypoxia-induced myocardial changes, two hypotheses are discussed: a release of phosvitin phosphate radicals ready for immediate utilization or a drug action mediated via a membrane-bound intrinsic proteinkinase system.