Mastitic milk is known to degrade hydrogen peroxide at a higher rate than milk from healthy cows due to increased enzymatic, i.e. catalase, activity. This work deals with a feasibility study of a new method for monitoring hydrogen peroxide degradation in milk based on the electrochemical detection of hydrogen peroxide. This technology could be implemented in-line with the milking equipment at farms. A low pasteurised (75 °C/15 s), non-homogenised milk was chosen as a model for fresh milk. Milk samples were spiked with catalase (0.53-5.33 U/ml). Given that H2O2 as a parameter allows for the early indication of mastitis (in itself or in combination with other measurements), we believe that the SIRE technology could be developed further to meet the analytical requirements of such a detection system. © 2004 Elsevier Ltd. All rights reserved.