Methylxanthines in the form of coffee and tea may be dietary factors that function as pharmacologic bronchodilators. To examine this hypothesis, we analyzed data from the Second National Health and Nutrition Examination Survey (NHANES II). NHANES II was conducted on a sample representative of the civilian noninstitutionalized US population, which included white and black adults aged 30 years or older. We examined the relationship of usual coffee and tea consumption from a medical history questionnaire to the presence of asthma and wheezing symptoms. Subjects who drank coffee on a regular basis had a 29% reduction in the odds of having current asthma symptoms (odds ratio, 0.71; 95% confidence interval, 0.55 to 0.93) when compared with non-coffee drinkers. The effect exhibited a significant dose-response relationship, with the number of cups of coffee consumed per day being inversely related to asthma prevalence. This relationship was independent of age, gender, and cigarette smoking. Tea consumption was not significantly related to asthma prevalence in this cohort.