Type 2 diabetes (T2DM) is now a pediatric disease. As in adults, it disproportionately affects ethnic and racial minorities, including Hispanics. The preponderance of Hispanics in south Texas are of Mexican American (MA) heritage. Over the past 16 years, we have accumulated a large cohort of children with diabetes. We have noted distinct differences in numerous parameters between MA children with T2DM and those with type 1 diabetes (T1DM). In order to explore these observations, we have reviewed the records of all children diagnosed with diabetes (n = 669) during the 9 years between January, 1990 and December, 1998 and seen by our pediatric diabetes group. In this cohort were 329 MA, 287 non-Hispanic whites (EA) and 53 African Americans. Compared to EA children with T1DM, MA children were more likely to have a parent with diabetes, to be hospitalized at the time of diagnosis and to lack health insurance. The differences between MA children with T1DM and T2DM were significant: specifically, children with T2DM were more likely to be female and pubertal with a body mass index >25 kg/m(2) and have acanthosis nigricans. Slightly more than 2/3 of the MA children with T2DM had at least one parent already diagnosed with T2DM. Less than 1/3 of the children with T2DM required hospitalization at the time of diagnosis and only a 1/4 have private health insurance. Over this 9-year interval, the apparent incidence of diabetes almost tripled in south Texas with the great majority of that increase due to the increasing numbers of children with T2DM.