Acculturation discrepancy theory predicts that conflicting cultural preferences between adolescents and their parents will increase the adolescents' risk for behavior problems such as substance use. This study evaluated this hypothesis in a sample of 1683 Hispanic students in Southern California who completed surveys in 9th and 10th grade. Measures included the students' own cultural orientations and their perceptions of their parents' preference for their cultural orientations ("Perceived Parental Cultural Expectations"--PPCE). Hispanic PPCE in 9th grade was a risk factor for lifetime, but not past-month, cigarette, alcohol, and marijuana use in 10th grade. The adolescents' own Hispanic orientation in 9th grade was protective against lifetime and past-month smoking and marijuana use and lifetime alcohol use in 10th grade. The effects of the acculturation variables did not vary according to generation in the U.S. Change in acculturation between 9th and 10th grade was statistically significant but small in magnitude. Increases in parent-child Hispanic acculturation discrepancy (i.e., the difference between the adolescents' own cultural orientations and their PPCE, with adolescents perceiving that their parents wanted them to be more Hispanic oriented than they actually were) from 9th to 10th grade were associated with an increased risk of substance use. Family-based interventions for acculturating Hispanic families may be useful in decreasing the likelihood of substance use among Hispanic adolescents.