The effects of a 100 g/kg substitution of guar gum on the body-weight gain, food consumption and faecal dry weight of mice fed on a high-sucrose diet and on the activities of hepatic glucose-6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44), malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+) (EC 1.1.1.40), ATP-citrate (pro-3S)-lyase (EC 4.1.3.8), 6-phosphofructokinase (EC 2.7.1.11), pyruvate kinase (EC 2.7.1.40) and fructose-1, 6-bisphosphatase (EC 3.1.3.11) were studied. Guar gum had no effect on body-weight gain or food consumption but increased faecal dry weight. Guar gum increased the activities of glucose-6-phosphate dehydrogenase, malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+) and 6-phosphofructokinase expressed on a wet-liver-weight basis. Guar gum increased the activities of glucose-6-phosphate dehydrogenase, malate dehydrogenase (oxaloacetate-decarboxylating)(NADP+), ATP-citrate (pro-3S)-lyase and 6-phosphofructokinase expressed on a liver-protein basis. Guar gum increased the activities of glucose-6-phosphate dehydrogenase and malate dehydrogenase (oxaloacetate-decarboxylating)(NADP+) expressed on a body-weight basis. These results suggest that guar gum increases the flux through some pathways of hepatic lipogenesis when mice are fed on high-sucrose diets.