['Language barriers between patients and providers may influence the process and quality of care.', 'To examine the association of language preference with length of stay (LOS) and in-hospital mortality for patients admitted for acute myocardial infarction (AMI).', 'Electronic administrative hospital discharge data for all non-disabled Medicaid beneficiaries age 35 years and older admitted to all acute care California hospitals with a diagnosis of AMI between 1994 and 1998.', 'We used multivariate regression to explore whether observed differences in the hospital LOS and in-hospital mortality between non-English preference (NEP) and English preference (EP) individuals could be explained by individual and/or hospital level factors. We adjusted for patient level characteristics using 24 covariates from a previously validated prediction model of mortality after hospitalization for AMI.', 'Of 12,609 Medicaid patients across 401 California hospitals, 2,757 (22%) had NEP. NEP was associated with a 3.9% increased LOS (95% CI 0.7, 7.1; p = 0.02) in unadjusted analysis and a 3.8% increased LOS (95% CI 0.3, 7.3; p = 0.03) after controlling for patient level characteristics. Differences in LOS were no longer significant after adjusting receipt of cardiac procedure/ surgery (2.8%; 95% CI -0.6, 6.2; p = 0.1) or after adjusting for hospital (0.9%; 95% CI -2.5, 4.3; p = 0.6). Non-English language preference was associated with lower in-hospital mortality in unadjusted analysis (odds ratio [OR] = 0.80; 95% CI 0.69, 0.94; p = 0.005), but was not significant after adjusting for patient level characteristics (adjusted OR [AOR] 0.95; 95% CI 0.78, 1.27; p = 0.6). Adjusting for receipt of cardiac procedure/ surgery (AOR 0.97; 95% CI 0.79, 1.18; p = 0.7) and hospital (AOR 0.97; 95% CI 0.78; 1.21; p = 0.8) did not alter this finding.'] Are acute myocardial infarction length of stay and hospital mortality associated with language preference?