The paper investigates the activities of the eight London Commissions of Sewers during the period 1800–47. It is argued that the criticisms of the Commissions made by Edwin Chadwick and later historians are undeserved. The Commissions were efficient, innovative and honest, and successfully kept pace with the ever-changing sanitary needs of the capital. Although they operated under severe statutory constraints, they constructed many miles of sewer and can be seen as the true instigators of the nineteenth-century sanitary revolution.