Although the number of enforcement actions against water suppliers to date has been limited, increasing regulation means that utilities are more likely to face US Environmental Protection Agency (USEPA) sanctions under the Safe Drinking Water Act and, to some extent, the Clean Water Act. In this article the author reviews possible criminal and civil actions--the latter consisting of administrative and court actions and citizens' suits--and briefly describes eight cases that exemplify various enforcement actions taken in the last few years. Large monetary penalties are not USEPA's usual goal in acting against a water supplier unless the supplier deliberately makes false reports. Instead, USEPA usually seeks to impose fines that match the amount a violator saved by not complying with regulations. Reorganization last fall at USEPA created the Office of Enforcement and Compliance Assurance, which indicates the agency's intention to streamline enforcement efforts. Includes 19 references.