PURPOSE:: The aim of the present study was to compare the effects of trehalose (TRE) and maltose (MAL) ingestion on exogenous carbohydrate oxidation rates and blood metabolite responses during prolonged moderate-intensity cycling exercise. METHODS:: Nine trained subjects performed three randomly assigned bouts of exercise separated by at least 1 wk. Each trial consisted of 150 min of cycling at 55% of maximal power output (Wmax) while ingesting a solution providing either 1.1 g.min TRE, 1.1 g.min MAL, or water (WAT). RESULTS:: Total carbohydrate oxidation rates were significantly higher (P < 0.05) in both the MAL (2.09 +/- 0.18 g.min) and TRE (1.92 +/- 0.32 g.min) trials compared with the WAT trial (1.62 +/- 0.28 g.min). Peak exogenous carbohydrate oxidation was significantly higher in the MAL trial compared with the TRE trial (1.01 +/- 0.24 and 0.73 +/- 0.22 g.min, respectively, P < 0.05). The MAL trial resulted in significantly reduced endogenous carbohydrate oxidation rates compared with the WAT trial (1.20 +/- 0.25 and 1.62 +/- 0.28 g.min, respectively, P < 0.05). When compared with the WAT trial, total fat oxidation for the same period was significantly reduced in both carbohydrate trials (0.91 +/- 0.19, 0.68 +/- 0.19, and 0.79 +/- 0.19 g.min for WAT, MAL, and TRE, respectively, P < 0.05) and tended to be lower in MAL compared with TRE (P < 0.06). DISCUSSION:: Both solutions maintained high plasma glucose concentrations. MAL had a "sparing" effect on endogenous carbohydrate stores. The reduced exogenous carbohydrate oxidation rate of TRE compared to MAL is probably due to a reduced enzymatic hydrolysis rate within the small intestine, causing a slower availability.