The cardiovascular-respiratory performance of the carp, Cyprinus carpio was evaluated during acute exposure to different concentration of lactic acid [1.5; 3.0 mmol/L] and for a varying periods [30; 60; 90 and 120 min.]. The most evident toxic response of lactic acid was a slowing of respiratory rate [hypoventilation] of the fish in comparison to the control values. A rapid drop in heart rate [reflex bradycardia] was observed after exposure of the fish to 1.5 mmol/L lactic acid. In contrast, an increase in heart rate [tachycardia] was recorded during exposure of fish to 3.0 mmo/L lactic acid. Cardiorespiratory synchrony was observed in this study. Changes in the heart rate was associated with a disturbances in the amplitude of P, QRS and T waves as well as the duration of P-Q and Q-T. On the other hand, the most striking changes in blood composition of carp after exposure to different concentrations of lactic acid were the immediate increase in red blood cell counts, plasma total protein, cholesterol, glucose and calcium while plasma sodium concentration was decreased. On the other side, plasma potassium concentration decreased rapidly to the lowest value by exposure for 30 min., thereafter it tended to increase gradually till the end of experiment. These changes in blood composition suggested that there was hypoxic stress due to acidemia. Finally, it is concluded that survival of the carp may be depended upon the ability of the cardiovascular-respiratory system to function under the effects of acidosis.