A high frequency (24%) of acute promyelocytic leukemia (APL) was noted among acute myelocytic leukemia (AML) cases at the Los Angeles County-University of Southern California (LAC-USC) Medical Center, in comparison with the expected frequency of 5% to 15%. Because of the high proportion of Latinos in this center, we questioned if APL is more common in this ethnic group. The proportion of APL among the 80 AML patients of Latino origin was significantly higher (30; 37.5%) when compared with the 62 non-Latinos (4; 6.5%) (P = .00001). In an attempt to verify this finding on a larger group of patients, we analyzed 276 pathologically verified cases of AML in patients aged 30 to 69 years from the entire County of Los Angeles, registered on an ongoing population-based epidemiologic study of AML. APL was more frequent among the 47 Latinos (24.3%) than in the 229 non-Latinos (8.3%) (P = .0075). APL is seen in younger patients with AML, but Latino AML patients also had a higher frequency of APL after accounting for their younger age (age-adjusted odds ratio for APL among Latinos in LAC-USC Medical Center, 9.4 [95% confidence interval (CI) 2.9, 30] P = .0002; among Latinos in the population-based study, 3.0 [95% CI 1.3 to 6.9] P = .01). The different ethnic distribution of AML was found to be due to a higher proportion of APL cases per se, and not to a lower proportion of any other French-American-British subtype (P = .0004). These results, from two different populations of AML patients, indicate that Latinos with AML have a higher likelihood of the APL subtype of disease, which may suggest a genetic predisposition to APL and/or exposure to distinct environmental factor(s).