The manual contains methods used by the U.S. Geological Survey to collect, preserve, and analyze waters to determine their biological and microbiological properties. It supplements ' Methods for Collection and Analysis of Aquatic Biological and Microbiological Samples ' (TWRI, Book 5, Chapter A4, 1977, edited by P. E. Greeson, T. A. Ehlke, G. A. Irwin, B. W. Lium, and K. V. Slack). Included are 5 new methods, a new section of selected taxonomic references for Ostracoda, and 6 revised methods.