Recruitment for this longitudinal study began in November 1983 and ended in July 1987. The initial visit consisted of an extensive interview to identify and to exclude those individuals with laboratory animal allergy, asthma, and other manifestations of allergy and to obtain an occupational history. Venipuncture was used to obtain serum for IgE and IgG antibody assays. Pulmonary function tests, including a methacholine challenge, were administered. Psychosocial questionnaires were administered. Subjects were evaluated at six month intervals with skin tests, venipuncture, and methacholine challenge. The degree of exposure to animal allergens was quantitated by aeroallergen sampling of workplace and personal breathing zone air and by work diaries.