The literature emphasizes that achievement motivation depends on a generalized desire to accomplish a given task; it does not deal with the issue of whether or not a culture values the appropriate behavior. This study investigated possible cultural and sex differences in achievement motivation from a bicultural perspective. This research: (1) examined and compared the incentive for achievement motivation of 480 fourth and sixth grade Mexican-American and Anglo-American students in three diverse school districts in California; and, (2) examined the relationship between language dominance as a possible indicator of acculturation and mode of achievement motivation. The results indicated a statistically significant difference between Mexican Americans and Anglo Americans and between males and females in mode of achievement motivation. Unexpectedly, in the academic setting, Anglo-American females showed a relatively lower need to achieve for self than Mexican-American females. The results from the language usage assessment indicated that sex was a more reliable predictor of achievement motivation than language dominance. The educational implications of this study are discussed. (Author/AMH)