The purpose of this investigation was to determine the effect of solute carbonation and carbohydrate (CHO) concentration on gastric emptying during prolonged cycling. Eight highly trained male cyclists completed four two hour cycling bouts during which one of four test solutions were consumed. The test solutions consisted of a carbonated 10 % CHO solution (CK), a non-carbonated 10 % CHO solution (NCK), a carbonated non-CHO solution (CNK), and a noncarbonated non-CHO solution (NCNK). Approximately 150 ml (8.5 ml/kg/hr) of one of the test solutions were consumed every fifteen minutes. The first 105 minutes of each trial was a continuous ride on an electrically braked cycle ergometer at 70 % V02 max. The last fifteen minutes of each trial was a self paced "performance ride" on an isokinetic cycle ergometer. The subjects were instructed to complete as much work (kilojuoles) as possible during the performance ride. Gastric contents were aspirated within five minutes following the performance ride and analyzed to determine the amount of the original test solution emptied.Of the original1273 ml ingested during each trial, the volumes emptied were 993.6 ±78.1, 1064.6 ±75.3, 1097.4 ±94.2, and 1147.2 ±95.9 ml (±SE) for CK, NCK, CNK, NCNK, respectively. The only significant difference was between trials CK and NCNK (P < 0.05). There were no statistically significant differences in total work output between any of the trials. However, when the performance data from the CHO trials were pooled and compared to the combined data from the non-CHO trials, total work output was significantly greater (P < 0.05) in the CHO group (1185.19 + 21.81, and 1092.85 + 21.52 Kj (+ SE) for the CHO and non-CHO groups, respectively). These data suggest that carbonated or 10 % CHO solutions, independent of one another, may not significantly inhibit gastric emptying. They also suggest that there may be some interaction between carbonation and CHO concentration which caused an additional inhibition of emptying. In addition, the potential for improved performance exists with the consumption of 10 % CHO solutions.