We investigated the relationship between home allergen exposure and decline in FEV1 in 10 asthmatic and 30 randomly selected, age-matched, nonasthmatic participants in the Normative Aging Study. We defined asthma as subject-reported wheezing apart from colds, with either a physician's diagnosis of asthma or a methacholine PD20 FEV1 of 8.6 micromol or less. We examined the relationship between the annual decline in FEV1 and the concentrations of the cockroach (Blattella germanica) allergens Bla g 1 and Bla g 2, the dust mite (Dermatophagoides pteronyssinus and Dermatophagoides farinae) allergens Der p 1 and Der f 1, and the cat (Felis domesticus) allergen Fel d 1 in house dust specimens. Bla g 1 (-79.8 ml/yr, p = 0.0006) and Bla g 2 (-40.81 ml/yr, p = 0.0004) were significant predictors of decline in FEV1 after adjustment for age, smoking, and baseline FEV1. These results were unchanged after elimination of the asthmatic subjects from the analysis. We conclude that cockroach allergen levels in homes is a risk factor for accelerated decline in FEV1 independent of airway responsiveness.