With monitoring changes required by the US Environmental Protection Agency's 1989 coliform rule, the problems associated with coliform regrowth in finished drinking water are increasing. This article reviews the types of regrowth phenomena and the analytical evidence for regrowth in distribution system pipelines. It also considers factors that influence bacterial regrowth, including environmental factors, bacterial nutrients, disinfectant residuals, corrosion and sediment accumulation, and hydraulic effects. Methods for controlling bacterial regrowth, including effective treatment and monitoring, flushing and mechanical cleaning, disinfection, corrosion control, and nutrient control, are examined, and the advantages of--and concerns about--using biological treatment are discussed. Includes 166 references, figures.