Neural networks have been developing into a valuable tools for chemists. Feed-forward, back propagation (FF-BP) neural networks have been most commonly used in a "regression-like" mode to derive models in chemical data, (known outputs are "taught" or "learned" by the neural network from input parameters). The program WinNN32 is a user friendly, shareware program for Windows 95/NT (only) that is useful to learn the details of FF-BP neural networks.