OBJECTIVE Administration of alkalinizing agents has been shown to improve performance in high intensity exercise. The present investigation was undertaken to determine whether sodium citrate ingestion enhances supramaximal endurance performance on a cycle ergometer and to assess its effect on oxygen debt incurred for the same supramaximal energy output. METHODS Ten untrained, healthy, males performed acute intense bicycle ergometry exercise in two sessions viz., without (control) and with sodium citrate ingestion (experimental) in a dose of 0.5 g/kg body weight. Pre-exercise O2 consumption, pulse rate (PR) and respiratory rate (RR)/minute were recorded before both sessions. Exhaustion time (ET) was noted and work done calculated in the control session. Post-exercise PR and RR/min were also recorded in both sessions of study. Venous blood samples were drawn post-exercise and analysed for pH and lactate. O2 debt incurred was calculated in both sessions. RESULTS Work output in supramaximal exercise averaged 69.40 +/- 15.31 Watts in the control session. None of the subjects in the experimental session complained of fatigue even when the exhaustion time noted in the control session was reached. Post-exercise tachycardia and tachypnoea were both significantly less (P<0.05 and P<0.001 respectively) in subjects after the experimental session as compared to the control. O2 debt incurred and lowering of blood pH were also significantly less (P<0.001) in the post-citrate phase. However, serum lactate increased significantly (P<0.05) in subjects after the experimental session. CONCLUSIONS Ingestion of sodium citrate prior to supramaximal exercise resulted in a reduction in post exercise O2 debt incurred. Blood pH was almost normal despite a higher serum lactate concentration. This probably led to an enhancement in exercise performance.