Originally confined to ineffectual civil measures, enforcement of environmental statutes now includes criminal sanctions, although only water pollution statutes have thus far produced a sizable body of criminal law. This article focuses primarily on the Federal Water Pollution Control Act (Clean Water Act) of 1976-1978 and the Rivers and Harbors Act of 1899. The few criminal cases decided under the Clean Air Act and the Federal Insecticide, Fungicide, and Rodenticide Act of 1976-1979 are also briefly discussed, with comments on the Toxic Substance Control Act of 1976-1979 and the Resource Conservation and Recovery Act of 1976-1978. Based on citations from relevant judicial decisions, the elements of an offense under the Clean Water Act are listed and defined, including such terms as discharge, navigable waters, point source, and person (the latter concept extended to corporate bodies). Oil and hazardous substance discharges are also quantitatively and qualitatively clarified. Further discussions cover the concept of criminal intent as a requirement for imposing criminal penalties on environmental law violators. Such related issues as scope of liabilities and defenses available to environmental law violators are also examined. Applicable judicial decisions are cited in numerous footnotes.