The case study attempts to assess the impact of agricultural pesticides on the aquatic environment of the San Joaquin Valley, and to point out some possible courses of action. The following approaches were used: University scientists and officials of federal, state, and county agencies were interviewed for information and expert opinions; the literature of pesticides was surveyed and reviewed, relying primarily on the unique collection, files, and services of the Environmental Toxicology Library of the Food Protection and Toxicology Center at the University of California at Davis; information of pesticide use was retrieved from a data bank containing files of detailed records in machine-readable form.