Treatment of opportunistic infections emerging in collagen diseases is very important as well as the therapy of original diseases. Lung tuberculosis, Pneumocystis carinii and lung fungal infections are main opportunistic infections. There is effective prophylaxis against them, though the cases for their administration should be carefully chosen because of their adverse effects. We have administrated INH and ST (Sulphomethoxazole and Trimethoprim) more than 15 years as the prophylaxis against tuberculosis and P. carinii to the cases who are treated more than 60 mg of prednisolone per day as an initial dose until less than 30 mg per day and completely succeeded. Infliximab treatment has been reported that it often induces tuberculosis in abroad and lots of occurrence was anticipated in Japan where high incidence of tuberculosis is observed. So far, however, there are only few patients, maybe due to the selection of the patients and actively utilizing prophylaxis.