Estimates of zooplankton biomass were made by use of a LECO Carbon Analyzer. The methodology developed in this study is a rapid, precise and accurate measurement of total carbon. Casein and benzoic acid were used interchangeably as standards. The technique was further tested on Tigriopus californicus which yielded a value of 38.6% C by weight. Estimates of total, living, and dead zooplankton biomass were made in a joint experiment by carbon analysis and ATP-C measurements. Field studies in Monterey Bay demonstrated a definite seasonal trend over the period of three cruises.