Data generated by the authors' field research on the bisexual and homosexual behaviors of men of Mexican origin living in southern California are presented and compared with the same behaviors of Anglo men in California and Mexican men in Mexico. Preferences for playing either the anal receptive or insertive sexual role and a focus on anal intercourse by unacculturated and less acculturated men of Mexican origin who have sex with men are the sexual behaviors judged to be most significantly different from Anglo men who have sex with men in California. Sexual socialization and acculturation were found to be the most important determinants of whether an individual's adult patterns of homosexual behavior will be more or less influenced by Mexican or Anglo homosexuality in spite of the length of time they may have lived in California. Evidence is presented about the effects that acculturation, preference for a sexual role in anal intercourse, and endogamy have on the spread of the AIDS virus in the Mexican origin population in California.