The need for a simple, objective and reproducible numeric scale to represent water quality in terms that all types of user will accept has been apparent for the last twenty years. Subjective classifications of water quality have been made, but they are seldom reproducible and lack sensitivity. Now, a new family of water quality indices has been developed that can be used either independently or in combination which promise to overcome previous criticisms. They are currently being used by a UK water authority to assess their utility to personnel responsible for both the planning and day-to-day management of surface water quality.