Spirometry reference values were determined for blue collar workers not exposed to any occupational respiratory hazards. The purpose was to provide a reference comparison population for the study of occupationally related lung diseases. A total of fourteen facilities comprising three major industrial groups were assessed including food products, synthetic textile mills, and electrical equipment. Persons exposed to dust or known respiratory irritants were excluded from the study. Persons with significant histories of dust or respiratory irritant exposures were also excluded. Evaluation included a personal history of respiratory symptoms and occupational background and measurement of the forced vital capacity (FVC), forced expiratory volume in 1 second, peak flow, and maximal expiratory flow rates at 50 and 75 percent of the FVC. The data were analyzed using a model fitting technique that incorporated values for race, sex, smoking status, and age group. Prediction equations for the variables included in the model were described in an appendix. The data obtained was comparable to that of other published studies on normal subjects. The authors conclude that biases imposed by the described technique are minimal.