Several parameters, such as total suspended solids, chemical oxygen demand, and parameters related to the plant operation (intensity of radiation of the lamps and transmittance) have been used as operational indicators of the disinfection efficiency of a secondary effluent from a wastewater treatment plant using UV radiation at 253.7 nm. The results obtained were statistically analysed to establish the correlations between the quality parameters of the influent and the operational conditions of the lamps, under standard conditions of the influx water. A significant (P<0.001) relationship was found between lamp radiation intensity and the radiation obtained by the microorganisms.