The effect on muscle glycogen utilization of drinking a glucose polymer solution before and during a soccer match was studied. Ten male soccer players were divided into two groups balanced both for playing position and between the two teams. Five players on the experimental team (ET) ingested 0.5 L of 7% glucose polymer solution 10 min before the game and at half-time. Five control team (CT) players ingested equal volumes of placebo at the same times. The players were biopsied in the vastus lateralis before and after the game. The change in muscle glycogen was less (p less than 0.01) in ET (111 +/- 24 mmol glucose units.kg-1 dry muscle) than in CT (181 +/- 24 mmol.kg-1). Blood glucose concentration was not changed after the game in either group. This study demonstrates that glucose ingestion reduces net muscle glycogen utilization in a field setting, i.e. soccer match play.