XROTOR is an interactive program for the design and analysis of ducted and free-tip propellers and windmills. It consists of a collection of menu-driven routines which perform various useful functions such as: Design of minimum induced loss rotor (propeller or windmill); Prompted input of an arbitrary rotor geometry; Interactive modification of a rotor geometry; Twist optimization of an arbitrary rotor for minimum induced loss; Analysis of a rotor with a wealth of choices of operating parameters; Incoming slipstream effects (from an upstream propeller, viscous wake...); Multi-point parameter display; Structural analysis and corrections for twist under load; Acoustic analysis with dB noise footprint predictions; Interpolation of geometry to radii of interest; Plotting of geometry, aerodynamic parameters, and performance maps. See also the QPROP web page.