Today's modern fighter design, with multifunction nozzles, is placing an increased emphasis on nozzle/airframe integration. The current tools available to the aircraft designer for aft-end design and evaluation are model test reports, being disseminated mainly by government laboratories, and three-dimensional numerical computation codes. Test data utilization usually is limited by the suitability of the area that has been tested. The second approach, analysis, usually requires time-consuming three-dimensional configuration data input. Recognizing the need for a quicker means of solution, useful in a preliminary design environment, a semiempirical computer methodology for determining three-dimensional aircraft afterbody performance has been developed. The essence of the approach is to construct equivalent bodies of revolution of three-dimensi onal bodies and then to utilize a straight or hybrid axisymmetric analysis. This approach has been developed for single- and twin-engine axisymmetric and two-dimensional afterbodies. The methodology has been verified by comparisons of afterbody drag and axial and longitudinal pressure distributions.