Many are the steps involved un the delivery of the prescribed dose to a patient in radiotherapy and it is well known that to obtain an accuracy of ±5% for the dose in the target volume it is necessary to mantain the accuracy within ±3.5% in reference conditions. It has been reported that centres, which have benefied from an external check, show minor deviations from the prescribed dose, while larger deviations are found in those centre which had not participated to intercomparisons. In 1993 the Associazione Italiana di Fisica Biomedica (AIFB) started a mailed Fricke dosimetry intercomparison, co-ordinated by the University of Florence. The paper describes the network structure and the results obtained until now in 17 centres with a total amount of 43 beams. The mail dosimeter is a chemical dosimeter which has be irradiated by the participating centre in a water phantom with a PMMA holder following the procedure in use in the centre. The results underline the usefulness of the programme to mantain the desired accuracy in delivering the dose to the patients.