generation; SES by income and education; and obesity by body mass index (BMI). RESULTS: Mean and standard deviations of BMI (kg/m 2 ) were 25.964.4, 26.064.2, and 25.564.3 in men of Mexican American, Cuban American, and Puerto Rican origin, respectively. For women, the corresponding values were 26.665.8, 25.965.0, and 26.265.9. Linear regression models of BMI which included acculturation, income, education, and other covariates were carried out. Income and education were not associated consistently with BMI. Acculturation, but only among Mexican Americans, was associated with BMI. Speci®cally, greater preference for English was associated with reduced BMI among women (P`0.01). Also, men and women of the second (P`0.001 in both sexes) and third (P`0.01 in men and P`0.001 in women) generation had greater BMIs. Relative to the ®rst generation, the increase in BMI units was 1.1560.34 in men and 1.7660.39 in women in the second generation and 0.8360.31 in men and 1.8360.37 in women of the third generation. CONCLUSIONS: BMI was not associated with SES, an unexpected ®nding since the relationship is generally negative in women from developed countries. The relationship between BMI and acculturation was weak and conditional. BMI in Mexican Americans appeared to be somewhat more sensitive to the process of acculturation than among Cubans or Puerto Ricans.