Summary: The Environmental Protection Agency (EPA) has not effectively fulfilled its responsibility to provide reference standards (precisely defined samples) of pesticides for use by the Food and Drug Administration (FDA). As a result, the FDA is seriously hampered in monitoring pesticide residues in food and in enforcing pesticide tolerances. The Pesticide Reference Standards Section (PRSS), which provides regulatory agencies with samples of precisely defined composition for use in analysis of food for pesticide residues, was transferred from the FDA to EPA. After the transfer, the laboratory in which PRSS was located was closed. PRSS staff remained in administrative offices at the laboratory and continued to provide previously partitioned reference standards on request. The laboratory was moved and limited operations were resumed in February 1978. During its 18-month closure, PRSS exhausted its inventory of many standards and, therefore, was unable to provide some needed standards to FDA and provided some others that were either degraded or subpotent. The PRSS inability to provide pure, potent reference standards when needed seriously impairs the enforcement programs of other agencies. The Administrator of EPA should take whatever actions are necessary to: perform appropriate tests to assure that standards sent to enforcement agencies are of the proper quality; and enable PRSS to accomplish its other tasks, including data compiling and cataloging, indexing, synthesizing, and purifying standards materials.