We have performed a 4-yr prospective survey of the association of allergen skin test positivity, total serum immunoglobulin E (IgE), and bronchial responsiveness to methacholine, with longitudinal decline in FEV1, in subjects over 65 yr of age. In 1987, 324 subjects completed a respiratory questionnaire, and underwent measurement of FEV1 and FVC, methacholine challenge, skin prick testing (to Dermatophagoides pteronyssinus, cat fur, mixed grasses, and Aspergillus fumigatus) and estimation of total serum IgE. After an interval of 4 yr, 212 subjects were reexamined. The mean annual decline in FEV1 was significantly higher in males than in females, but was not significantly influenced by smoking habits defined at the start of the study. The relation of atopy (skin test reaction to allergen > or = 3 mm greater than saline control), increased bronchial responsiveness (PD20FEV1 < or = 6.4 mumoles methacholine) and serum IgE > 80 IU/ml, to annual decline in FEV1 was examined for each risk factor individually with adjustment for age, sex, height, and initial FEV1, by multiple linear regression. Both atopy and bronchial responsiveness were significantly associated with accelerated decline in FEV1. Elevated IgE was correlated with faster FEV1 decline in subjects who were current smokers at the start of the study. In a multiple regression model examining the mutually adjusted associations of all relevant variables with annual decline in FEV1, male sex was the most important predictor (B = 38.6 ml/yr, 95% Cl = 4.3, 72.9). Increased bronchial responsiveness also tended to be associated with accelerated decline in FEV1. In further analyses incorporating the same variables, but restricted to specific smoking categories, age was the only significant factor in the never-smokers, whereas both atopy (B = 44.5 ml/yr, 95% Cl = 3.8, 85.3) and increased bronchial responsiveness (B = 43.5 ml/yr, 95% Cl = 4.6, 82.3) were significant predictors of accelerated FEV1 decline in former and current smokers combined.(ABSTRACT TRUNCATED AT 250 WORDS)