Objective: To compare demographic and clinical characteristics among 3 ethnic groups of indigent patients exhibiting diabetic ketoacidosis DKA), in Houston, Texas. Methods: Over a span of 3.5 years, 321 patients were interviewed at the time of admission for DKA. Demographic, clinical, and biochemical data and measures of pancreatic beta-cell function were obtained at baseline and during follow up. Pearson's chi-square test, or one-way ANOVA, were used, as appropriate, to evaluate group differences. Results: Of the 321 subjects, 44% were African-Ameri-can, 40% were Hispanic, and 16% were Caucasian. A significantly higher proportion of Hispanics had preserved beta-cell function, compared to African Americans and Caucasians (51% vs 32% and 32%, respectively; P=.002). This difference, present at the time of the admission, was maintained through follow up. in a multivariate analysis, Hispanic ethnicity (OR 3.61; 95% Cl 1.48-9.29) was a significant predictor of preserved P-cell function. In addition, Hispanics were less likely to develop DKA as a result of treatment noncompliance, and more likely to have DKA precipitated by an acute illness. Conclusions: Our findings indicated that ethnicity is associated with significant differences in the pathophysiologic and clinical characteristics of indigent, ketosis-prone patients. Hispanic ethnicity was found to be associated with greater P-cell functional reserve, and less dependence on chronic insulin therapy.