Background Primary percutaneous coronary intervention (PCI) has become an important treatment for patients (pts) with acute myocardial infarction (AMI). Whether ethnic and socioeconomic disparities exist in use of primary PCI for AMI is unknown. Methods Patients hospitalized for transmural AMI in Pennsylvania from January 2003 through June 2004 (n = 16985) were studied. Patient clinical characteristics, insurance status, and hospital type were analyzed using multiple logistic regression analysis to assess the independent correlates of PCI on the day of admission for AMI. Results Among 16985 pts, primary PCI was performed in 6934 (46%) of 14944 whites, 363 (40%) of 910 African Americans, and 618 (55%) of 113 1 other ethnicities. Primary PCI was associated positively with younger age, male sex, known dyslipidemia, and prior PCI (all P <.03), and negatively with diabetes, renal failure, prior myocardial infarction or bypass surgery, and higher predicted death by the Mediqual Atlas Outcomes score (all P <.01). After adjustment for these variables, African American ethnicity (odds ratio 0.78, 95% confidence interval 0.67-0.91), lowest income quintile, (odds ratios 0.87, 95% confidence interval 0.80-0.94), lack of commercial insurance, and nonurban and for-profit hospital status were independently associated with not undergoing primary PCI (all P <.003). Conclusion In a large statewide database of pts with ST-segment elevation AMI, primary PCI was used less often in African American and in lower-income pts, independent of clinical, hospital, and insurance characteristics, identifying persisting disparities in application of advanced cardiac care in traditionally underserved segments of the population.