Oncolor, the French regional cancer network of Lorraine, proposes clinical guidelines for the diagnosis, the treatment and the follow-up of cancers. In addition to paper documents, two computerized supports, a web site and the Kasimir software have been developed to make the use of these guidelines and their updating easier. This study aims at evaluating these three tools in breast and prostate cancer and to determine if computerized supports provide an additional help and an added value. From May to July 2001, 25 physicians of the Oncolor network have analysed, by consulting the guidelines on each of the 3 supports, 23 clinical cases of breast cancer and 22 cases of prostate cancer, i.e. in total 1,293 cases. We observe for breast cancer a response rate consistent with the guideline significantly higher with the Kasimir software compared to paper (87.1% versus 77.8%) or to Internet (87.1% versus 75.8%), an optimisation of the recourse to a specialised physician or a pluridisciplinary committee and globally a good satisfaction of the users. These results induce us to continue with the Kasimir experiment, to develop it for other cancers, especially those with a complex management and to evaluate its impact on medical practices.