This article summarizes results of research on the rehabilitation of clogged extraction wells in the Netherlands by KIWA, the Netherlands Waterworks Testing and Research Institute. Types of well clogging identified include clogging by accumulation of iron oxides and biomass, clogging caused by anaerobic geomicrobiological processes, and accidental clogging caused by fine sand, silt, or both. Causes, symptoms characteristic of the causes, mechanical or chemical rehabilitation, and measures to prevent clogging are addressed. Results indicate that well clogging characterized by entrance resistance occurs only in wells that extract aerobic groundwater, whereas well clogging without entrance resistance occurs only in wells that extract anaerobic groundwater. Monitoring drawdown in order to proceed with rehabilitation, the cost of rehabilitation, and safety precautions during rehabilitation are also discussed. Includes 25 references, table, figures.