BACKGROUND: Patient-physician race/ethnicity and language concordance may improve medication adherence and reduce disparities in cardiovascular disease (CVD) by fostering trust and improved patient-physician communication. OBJECTIVE: To examine the association of patient race/ethnicity and language and patient-physician race/ethnicity and language concordance on medication adherence rates for a large cohort of diabetes patients in an integrated delivery system. DESIGN: We studied 131,277 adult diabetes patients in Kaiser Permanente Northern California in 2005. Probit models assessed the effect of patient and physician race/ethnicity and language on adherence to CVD medications, after controlling for patient and physician characteristics. RESULTS: Ten percent of African American, 11 % of Hispanic, 63% of Asian, and 47% of white patients had same race/ethnicity physicians.24% of Spanish-speaking patients were linguistically concordant with their physicians. African American (46%), Hispanic (49%) and Asian (52%) patients were significantly less likely than white patients (58%) to be in good adherence to all of their CVD medications (p<0.001). Spanish-speaking patients were less likely than English speaking patients to be in good adherence (51%versus 57%, p<0.001). Race concordance for African American patients was associated with adherence to all their CVD medications (53% vs. 50%, p<0.05). Language concordance was associated with medication adherence for Spanish-speaking patients (51% vs. 45%, p<0.05). CONCLUSION: Increasing opportunities for patient- physician race/ethnicity and language concordance may improve medication adherence for African American and Spanish-speaking patients, though a similar effect was not observed for Asian patients or Englishproficient Hispanic patients. © Society of General Internal Medicine 2010.