Examines the estimation accuracy of a group of parametric cost models used for a variety of spacecraft. For two major reasons, it reinforces the caveat of model builders that models should not be used mechanically but should reflect changing spacecraft characteristics: (1) weight, the most widely used independent variable, should be less constraining in the next generation of spacecraft with space-shuttle launching; and (2) spacecraft are becoming cheaper on a per-unit-of-performance basis. In estimating nonrecurring costs, none of the models are generally applicable to any subsystem except structure, but several SAMSO models are useful for estimating total nonrecurring cost. All the models do better in estimating recurring costs. The SAMSO models appear most reliable for the user who lacks detailed knowledge of a program and wishes to base an estimate on such characteristics as weight and maximum array output.