Description or discrimination of boundary curves (shapes) is an important problem in picture processing and pattern recognition Fourier descriptors (FD's) have interesting properties in this respect. First, a critical review is given of two kinds of FD's. Some properties of the FD's are given and a distance measure is proposed, in terms of FD's, that measures the difference between two boundarv curves. It is shown how FD's can be used for obtaining skeletons fobjects. Finally, experimental results are given in character recognition and machine parts recognition.