Based on oral glucose tolerance testing, the prevalence of diabetes in Australian adults has ranged from 2.3% in Europids in 1966 to 20% in small surveys of Aborigines. We have surveyed Aborigines and Europids simultaneously for further comparison of diabetes prevalence between these population groups. The samples were drawn from two adjacent country towns in south-eastern Australia, where Aborigines and Europids have been in contact for 150 years. By the 2-h (post-75 g oral glucose load) criterion (venous plasma glucose greater than or equal to 11.1 mmol/l), the crude prevalence of diabetes among 306 Aborigines was 7.8%, significantly higher than the 3.4% among 553 Europids (P less than 0.01). The prevalence of impaired glucose tolerance was similar in both groups (6.9% in Aborigines, 6.0% in Europids, no significant difference). Adjustment for the marked differences in age distribution between Aborigines and Europids by direct standardization to the 1980 world population increased the apparent differences, with the finding of a four-fold greater prevalence among Aborigines (8.1% compared with 1.9%). The greater frequency of glucose intolerance among Aborigines appears to persist despite the higher proportion of Europid genetic mix with these urbanized south-eastern groups than with Aborigines from remote settings.