The need for mass prediction methods and the problems associated with them are discussed. Two methods for wing mass prediction are then presented, one based on an analysis of empirical data and the other having a theoretical basis. The two methods have been rested against a substantial number of actual wing masses covering all types of aircraft. Overall the results are acceptable although there are some, specific, discrepancies. While the empirical method is easier to use and actually shows less scatter, the theoretically based method does enable particular features of the wing design to be allowed for and gives somewhat better correlation with actual wing masses.