Estimates of body surface area were made based on measurement of 81 subjects, ranging from premature infants to adults. SA was calculated geometrically for each subject from 34 body measurements, and the values obtained compared with those based on previously published formulas and graphs. The most widely used formula, that of Du Bois and Du Bois, increasingly underestimated SA as values fell below 0.7 m2; the disparity was greatest in the newborn infant (7.96%). Closer agreement was obtained with the equations and nomograms of Body, Brody, Faber and Melcher, and Sendroy and Cecchini, although minor deviations were noted in some age ranges. The formula SA (m2) = weight (kg)0.5378 X height (cm)0.3964 X 0.024265, derived from the measured data by multiple regression analysis, gave a good fit for all values of SA from less than 0.2 m2 to greater than 2.0 m2 (r = 0.998). This formula was used to construct nomograms for estimation of SA in infants, children, and adults from height (length) and weight.