Background and Purpose: This study compared the risk for stroke during acute myocardial infarction (AMI), percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass grafting (CABG) between Mexican Americans (MAs) and non-Hispanic whites. Methods: We examined the age-specific rate ratios (RR) of acute stroke during hospitalization for AMI, CABG and PTCA in a population-based study in Corpus Christi, Tex. by searching the cardiac surveillance data for ICD-9 codes for stroke (430–437). ICD-9 stroke codes were validated by comparing medical chart abstraction with ICD-9 discharge diagnoses. Results: Stroke codes were found in 220 of the 5,697 admissions for AMI, CABG and PTCA. In the 45- to 59-year age-group MAs had a RR of 2.66 (95% CI 1.36–5.23) relative to non-Hispanic whites. In the 60- to 74-year age-group the RR was 1.52 (95% CI 1.11–2.08). There were no significant differences in the 25- to 44-year age-group. These ethnic relationships were found in nondiabetics but not in diabetics. Women in the 45- to 59-year age-group had a RR of 1.88 (95% CI 1.09–3.25) compared with men, but there were no significant sex differences in the 25- to 44- or 59- to 74-year age-groups. Stroke ICD-9 codes have a poor positive predictive value for acute stroke ranging from 10 to 76%. The stroke misclassifications were nondifferential with respect to ethnicity or sex. Conclusions: MAs have a higher stroke rate complicating acute heart disease in Corpus Christi. A rigorous stroke surveillance project is needed to study the burden of stroke in MAs, the United States’ largest Hispanic population.