'State of the art' is described of the water quality parameter known as turbidity, particularly with regard to the effects of urbanization on a recreational water body. Field and laboratory data are presented which support a new broader definition for the parameter. For the general case, it is shown that turbidity is a composite parameter which is well related to apparent color, suspended solids concentrations, dissolved ion concentrations and the optical properties of suspended solids. The traditional relationships to B.O.D., D.O., CO2, total hardness, alkalinity, and pH are not challenged but rather are augmented. For the specific field case considered, it is shown that the degree of turbidity is related to the character and degree of urbanization, the natural geologic setting and the weather conditions.