This study evaluated the relationship between spirometric pulmonary function measures and air pollution and meterologic variables for adult asthmatic in-patients in an urban, long-term intensive treatment center. Two groups of 67 patients were studied during a late spring-summer period and a late fall-winter period. Patients were classified according to the role of allergic factors and the degree of airways hyperreactivity. In all analyses, 24-hour average levels of air pollution preceding pulmonary function measurement were related to subsequent 8:00AM pulmonary functions. Multiple linear regression analyses by leaps and bounds for individuals and groups, defined by reaginic factors and airways hyperreactivity, failed to identify a systematic effect for any air pollution variable upon any pulmonary function measure. The lack of any relationship does not appear attributable to limited exposure to air pollution variables, but may be affected by as-needed (PRN) medication usage, type of pulmonary function measurement employed, and periods selected for analyses. The relative strengths and limitations of the study are discussed.