An interactive computer program system has been developed which provides induced-drag analysis, optimization and configuration-design capabilities. The program system employs subsonic far-field (Trefftzplane) analysis, and novel mathematical formulations of the constrained optimization problems which are based on calculus of variations. The analysis and optimization technique, utilizing panel-method technology with piecewise quadratically varying bound-circulation, is fast, numerically stable and easy to use, and therefore is very suitable for interactive design piorposes in which rapid configuration trade-offs have to be made. The paper presents an outline of the induced-drag analysis and optimization technique, comparisons with other theories and the interactive design capability. Paper presented at the AIAA 21st Aerospace Sciences Meeting, January 10-13, 1983, Reno, Nevada.