Daily deaths are associated with air pollution. This association might be con*hhy;founded,by uncontrolled,risk factors. In order to estimate,the potential confounding,caused by respiratory epidemics,of the association between,air pollution and health effects, a time series study of air pollution and daily deaths was carried out. Daily records of deaths for all ages were obtained from five US cities: Chicago, IL; Detroit, MI; Minneapolis, MN; Pittsburgh, PA; and Seattle, WA. Daily levels of particles with a 50% cut-off aerodynamic,diameter,of 10 mm,(PM10) and,weather measurements,were,obtained. City-specific analysis was,carried out using Poisson regression, adjusting for time trend, ambient temperature, dew point, barometric pressure and day of the week. A cubic polynomial,was used for each epidemic,period ($10 days of excessive pneumonia hospital admissions), and a dummy variable was used to control for isolated epidemic,days. A 10-mg.m, before controlling for epidemics,and 0.78% (95% CI 0.51‐1.05) after. This study showed,that the association between,air pollution and daily deaths is not due to failure to control for influenza or pneumonia,epidemics. Eur Respir J 2000; 16: 723‐728. *Environmental Epidemiology Program, Dept of Environmental Health, Harvard, School of Public Health, Boston, MA, USA. **Environmental Pediatrics Pro- gram, Dept of Pediatrics, University of Santo Amaro, School of Medicine, Sa `o Paulo, Brazil. and ***Laboratory of Exp- erimental Air Pollution, Dept of Path-