Aluminium phosphide(AlP), a grain fumigant pesticide, was studied for its cardiotoxicity in anaesthetised rats. The hemodynamic and cardiac biochemical changes were investigated following intragastric administration of different doses of AlP (10, 20 and 40 mg). With 10 and 20 mg dose of AlP an immediate fall in BP was observed which recovered partially and stabilized for 10 minutes followed by a gradual fall till the animal died. However, with a higher dose (40 mg) there was no recovery in BP, instead the initial fall continued till the death of the animal. An increase in the heart rate was observed with 10 and 20 mg dose of AlP for 15 minutes which was followed by a marked fall till cardiac arrest ensued. On the other hand, 40 mg dose produced only a transient tachycardia followed by a prolonged bradycardia. ECG changes at all dose levels included initial tachycardia and ST segment elevation progressing to QRS broadening. However, marked conduction defects as evidenced by the ventricular ectopics were noticed only with 40 mg. The mean survival time dose dependently decreased with 10 mg(55 +/- 3 min), 20 mg(35 +/- 2 min) and 40 mg(18 +/- 2 min) of AlP. The cardiac glycogen, ATP and CP levels were significantly lowered in animals treated with 10, 20 and 40 mg of AlP. Higher levels of MDA in the cardiac tissue were observed with 10, 20 and 40 mg of AlP. Thus it is suggested that the deleterious effect of AlP on heart is mediated by both declined cellular metabolism of the myocardium as well as by necrosis of the cardiac tissue resulting in the release of reactive oxygen intermediates.