Milrinone is an inodilator drug. A phosphodiestrase type III (PDE III) inhibitor which has proven effective as an inotrope in cardiac patients of several categories even severe cases. In this study its safety on platelet functions in patients undergoing cardiac surgery has been investigated for the first 24 hours during and following emergence from CPB (cardiopulmouary bypass) since platelet functions is a detrimental factor in postoperative bleeding following cardiopulmonary bypass. Forty patients have been investigated divided into milrinone receiving group and control group and the effect on of platelet functions evaluated in both group and it was found that milrinone administration at 50 ug/kg loading dose and maintainace of 0.5 ug/kg/min had no effect on platelet functions beyond the effects of cardiopulmonary bypass itself and at this dose no excessive use of vasopressors inspite of being effective as a positive inotrope.