Maximum inspiratory pressure (MIP), an indicator of inspiratory muscle strength, is reported on 13,005 African-American and white participants from the Atherosclerosis Risk in Communities Study. Sex-specific associations between MIP and age, anthropometric measures, physical activity, health status, smoking status, and education level are presented. In this cohort of subjects 47 to 68 yr of age, MIP decreased 0.93 cm H2O (p </= 0.0001) in women and 1.2 cm H2O (p </= 0.0001) in men for each 1-yr increase in age. In both sexes, after adjusting for age, the associations between MIP and current body weight, weight at 25 yr of age, waist girth, body mass index, and calf girth were statistically significant and nonlinear (convex quadratic). MIP was positively associated with standing height in both sexes after controlling for age (p </= 0.03). The age-adjusted association between MIP and sitting height was nonlinear in men and linear in women. MIP was also associated (positively) with education level, health status, physical activity, and (negatively) cigarette smoking. The study was not designed to evaluate associations with race, but data patterns suggest the absence of a race effect on MIP.