Sewage oxidation ponds as used in southwestern United States may be described as shallow artificial basins designed to receive clarified sewage continuously for a nominal detention period of from 3 to 4 weeks and to provide a maximum photosynthetic action. Losses from percolation and evaporation are normally negligible in comparison to inflow. It is the purpose of this paper to discuss sewage oxidation ponds by presenting (1) performance data gathered during the past three years from municipal, army and navy installations in California, Nevada, and Arizona, (2) operating details and (3) design features.