Fifteen patients suffering from severe systemic diseases were treated with monthly pulses administration of cyclophosphamide (0.7 g/m2 of body surface): 8 acute systemic lupus erythematosus, 2 Wegener's granulomatous, 1 polyarteritis nodosa, 1 rheumatoid vasculitis, 1 progressive systemic sclerosis, 1 relapsing uveitis and 1 dermatopolymyositis. The indications for cyclophosphamide were: glomerulonephritis (6 cases), resistance to previous treatments (7 cases) and undesirable side effects of corticosteroid therapy (2 cases). After 3 pulses, the disease was controlled in 12 patients (80%) and corticosteroids could be decreased in all 12 cases without an evolutive relapse of the disease. Five patients developed infections (2 septicemia, 1 zona, 1 herpes gingival stomatitis and 1 viral meningitis) which were treated without sequelae. One patient developed cystitis with hematuria after the 3rd pulse; association of mesna, a urinary tract protective agent, enabled the continuation of treatment without a cystitis relapse. At the end of our retrospective study, the efficacy of pulse cyclophosphamide administration seems to be satisfactory but the risk of undesirable side effects should limit its use to severe systemic diseases or those resistant to conventional therapies.