An ecological baseline study was conducted on the Monterey breakwater. Qualitative and quantitative survey of the plants and animals occupying meter square quadrats along a cross-sectional transect covering the breakwater and the adjacent mud bottom out to depths of 13 meters was made. Overall, the differences between the populations of the inner and outer parts of the breakwater appeared minor and primarily involved differences in relative abundance of only a few species. Data from this study establish an ecological baseline for future studies on the Monterey breakwater.(Author).