We compared plasma glucose and insulin responses to an Aboriginal bushfood and its western equivalent in healthy Aborigines and Caucasians. Bush potato (Ipomoea costata), an Aboriginal bushfood which is slowly digested in vitro, and potato (Solanum tuberosum), which has a high glycemic index, were studied. The areas under the glucose and insulin curves for Aborigines were 34% and 42% smaller, respectively, after bush potato than after potato (p less than 0.05). In Caucasians only the insulin response to bush potato was lower (by 19%) than that to potato (p less than 0.05). Compared with Caucasians, Aborigines produced 2.5 times greater glucose and insulin responses to potato (p less than 0.025). Their insulin responses to bush potato were also twice as large (p less than 0.05) although glucose responses were not significantly different. These findings add weight to the hypothesis that rapidly digested carbohydrate in western diets may be one of the factors in the lifestyle change which precipitates diabetes in indigenous populations.