Abstract Morbid obesity and underweight have been reported to have separate and negative effects on pulmonary function. The purpose of this study is to determine whether the varied weights of a healthy black population studied for the development of pulmonary function standards might have separate, negative effects on their pulmonary function indices. The study included 335 black male and 529 black female adults between 18 and 85 years of age, and 82 and 340 pounds of weight. The Body Mass Index (BMI-W/H 2) was calculated as a measure of adiposity. Multiple regression analysis of the variables of interest (sex, age, smoking status, height, weight, and the BMI) was carried out, with lung function as the independent variable. The effect on each pulmonary function index varied by sex. In women, weight and the BMI contributed significantly to the total variance of three variables (inspiratory capacity (IC), expiratory reserve volume (ERV), and functional residual capacity (FRC)). Weight contributed more to the IC (positive association), while the BMI contributed more to the ERV (negative association), and both weight and the BMI contributed equally to the FRC (negative association). In men, however, weight and the BMI did not contribute significantly to the total variance for any pulmonary function variable. The significance of these effects of weight, the BMI, and body fat on pulmonary function are discussed in relation to similar studies in other populations, and to possible mechanisms of action. Needs for future investigation are defined.