Thames Water has developed a statistical method of analyzing the performanceof individual rapid gravity filters within a treatment works based on continuously monitored on-line turbidity data. The method minimizes the effect of backwash data, produces historic summary reports outlining filter performance, and in doing so, aids the early identification of under-performing filter beds. This paper describes this method of analysis and outlines the method currently being developed to analyze real-time rapid gravity filter run data from on-line turbidimeters. Includes 4 references, tables, figures.