Arm span has been proposed as a surrogate for standing height in the prediction of lung volumes in patients with thoracic deformities or who are unable to stand. The relationship between arm span and height has previously been reported as either a fixed ratio unaffected by age or as a regression equation in which the ratio varies as a function of age. We studied the relationship between standing height, arm span, race, sex, and age in 202 patients (ages 20 to 88 yrs) referred for screening spirometry. Multiple linear regression analysis found arm span, race, sex, and age to be predictive of standing height (r2 = 0.8659, p < 0.0001). Subgroup analysis revealed that age was a significant factor among males of either race, but not among females of either race. Fixed arm span to height ratios were also calculated for each group and may be used to estimate standing height with reasonable accuracy except at extremes of stature.