The Data Reporting Guideline (DRG) for Laboratory Studies of Pesticide Accumulation in Fish, Series 165-4, gives guidance to pesticide registrants on the format for their study report so that the Agency can review it efficiently. The guidance clarifies sections in the existing Pesticides Assessment Guidelines, Subdivision N, on data reporting. It provides an outline for the study report, describes the topics which should be addressed, and the presentation of the results of the study. Items which need to be addressed include, for instance, the water used; the test fish used (species, source, age, size and weight, etc.); the exposure method and its protocol; the depuration conditions and the protocol; the sampling protocol; and the analytical method. Data submitters can use the DRG in preparing their reports for submission to EPA to meet 40 CFR 158 requirements for the registration of pesticides. The DRG for Series 165-4, Laboratory Studies of Pesticide Accumulation in Fish, is one of a number of DRG's published by the National Technical Information Service as an addendum to Subdivision N of the Pesticide Assessment Guidelines.