This study observed the relationship between air pollutants and ischemic cardiac diseases such as angina and acute myocardial infarction in a representative cardiovascular center emergency room in São Paulo, Brazil. Daily emergency room admissions to the Institute of the Heart of the University of São Paulo, as well as data concerning daily air pollutant levels and meteorological variables, were collected from January 1994 to August 1995. Generalized additive Poisson regressions were fitted to the logarithm of the expected values of total emergency room visits due to angina or acute myocardial infarction, controlling for smooth functions of season and weather and indicators for days of the week. All investigated pollutants were positively associated with ischemic cardiovascular disease emergency room visits, and the time lags were relatively short, but only CO presented an effect that was statistically significant. An interquartile range increase in CO was associated with an increase of 6.4% (95% CI: 0.7-12.1) in daily angina or acute myocardial infarction emergency room visits. This result did not change when estimates were done using linear models and natural cubic splines. This study showed that air pollution has a role in cardiovascular morbidity in São Paulo, reinforcing the necessity for air pollutant emission-controlling polices in urban areas.