To determine the effect of the taurine containing drink "Red Bull" on cardiac parameters thirteen endurance trained subjects performed an exhaustive bout of endurance exercise at three different times. Prior to the exercise the original "Red Bull" drink, a similar drink without taurine, containing caffeine, and a "placebo" drink without caffeine and without taurine were ingested by the subjects in a double-blind cross-over design. Echocardiographic examinations were performed before the drinks, 40 minutes after the drinks prior to the exercise and in the regeneration period after exercise. Stroke volume was significantly influenced only in the "Red Bull group" (80,4+/-21,4 ml before drink vs. 97,5+/-26,2 ml in the regeneration period), mainly due to a reduced endsystolic diameter and volume. Furthermore in this group the peak late diastolic inflow (V(A)) in the regeneration period was significantly higher compared with the pre-exercise levels. This observation was also made in the caffeine group but without any consequences on ventricular function. The results of the present study show an influence of the original caffeine and taurine containing drink (Red Bull) on parameters of the cardiac contractility.