The recent growth in the production rate of digital side scan sonar images, coupled with the rapid expansion of systematic seafloor exploration programs, has created a need for fast and quantitative means of processing seafloor imagery. Computer-aided analytical techniques fill this need. A number of numerical techniques used to enhance and classify imagery produced by SeaMARC II, a long-range combination side scan sonar, and bathymetric seafloor mapping system are documented. Three categories of techniques are presented: (1) preprocessing corrections (radiometric and geometric), (2) feature extraction, and (3) image segmentation and classification. An introduction to the concept of ''feature vectors'' is provided, along with an explanation of the method of evaluation of a texture feature vector based upon gray-level co-occurrence matrices (GLCM). An alternative to the a priori texel (texture element) subdivision of images is presented in the form of region growing and texture analysis (REGATA). This routine provides a texture map of spatial resolution superior to that obtainable with arbitrarily assigned texel boundaries and minimizes the possibility of mixed texture signals due to the combination of two or more textures in an arbitrarily assigned texel. Computer classification of these textural features extracted via the GLCM technique results in transformation of images into maps of image texture. These maps may either be interpreted in terms of the theoretical relationships shown between texture signatures and wavelength or converted to geologic maps by correlation of texture signatures with ground truth data. These techniques are applied to SeaMARC II side scan sonar imagery from a variety of geologic environments, including lithified and nonlithified sedimentary formations, volcanic and sedimentary debris flows, and crystalline basaltic outcrops. Application of the above processing steps provided not only superior images for both subjective and quantitative analysis but also the critical ability to discriminate between outcrops with distinct lithologies but similar image intensity. ¿ American Geophysical Union 1989