An automated image analysis system for determination of myosin filament orientations in electron micrographs of muscle cross-sections is described. Analysis of the distribution of the orientations is important in studies of muscle structure, particularly for interpretation of x-ray diffraction data. Filament positions are determined by filtering with a point spread function that incorporates the local symmetry in an image. Filament orientations are determined by correlation with a template that incorporates the salient filament characteristics and the orientations classified using a Gaussian mixture model. Application to micrographs and comparison with manual classification of orientations shows that the system is effective.