Studies of relative levels of psychological distress among Mexican Americans and non-Hispanic Whites have found mixed results, possibly due to cultural differences within Mexican American samples which may confound potential ethnic differences. The hypothesis that differences in psychological distress between Mexican Americans and non-Hispanic Whites would be explainable by cultural variables (acculturation, years of residence in the United States) and social psychological variables (social integration, strain, social support, social conflict) was tested in a household probability sample of Mexican Americans born in Mexico (N=706), Mexican Americans born in the United States (N=538), and nonhispanic whites born in the United States (N=1,149). Interviews with respondents revealed that Mexican-American natives had the highest distress scores, followed by Mexican-American immigrants and then by non-Hispanic Whites Distress was regressed on the cultural and social psychological variables in each of the three groups. Financial strain was significantly associated with increased distress, and marital support with decreased distress, in all three groups. Although high financial strain and low marital support appeared to contribute to the ethnic difference in distress, the ethnic effect was still significant when these variables were controlled. Low social conflict in Mexican-American immigrants, possibly combined with selective immigration and differences in social comparisons, appeared to contribute to this group's advantage over Mexican-American natives. (Six pages of references, 1 data table, and 25 data bar graphs are included.) (Author/NB)