The purpose of this study was to develop and cross-validate an equation for estimating fat-free mass (FFM) in female ballet dancers. One hundred twelve, 11- to 25-yr old, female dancers had FFM measured by total body electrical conductivity (TOBEC) and anthropometrics, including skinfold and circumference measurements. The regression equation that best estimated FFM in the dancers was FFM = 0.73 x body weight (kg) + 3.0, (R2 = 88%, SEE = 1.5 kg, P < 0.001). This equation was then cross-validated on a separate group of 23 female dancers who also had FFM measured by TOBEC. FFM estimated by this equation correlated with FFM measured by TOBEC (r = 0.94, SEE = 0.9 kg), and the difference in the FFM values using the two methods (the equation and TOBEC) did not change with the size of the FFM of the dancers. FFM in accomplished female ballet dancers can be best estimated from body weight alone. This is related to the homogeneity of body size and body composition in female ballet dancers at this level.