SummaryCyclophosphamide was injected weekly, intravenously, in 26 cases of solid tumors and in 15 cases of malignant lymphomas and leukemias. Six patients of the first group and 10 patients of the second group showed an objective remission. Objective remissions were observed in patients with lung cancer (4 cases), malignant melanoma and ano-rectal carcinoma (1 case of each), Hodgkin's disease (5 cases), chronic lymphatic leukemia (3 cases) and reticulum-cell sarcoma (2 cases).With the dosage regimen used in this series, leukopenia was frequent and thrombocytopenia was uncommon. Nausea and vomiting were the most frequent side-effects. Drug toxicity was suspected to be the cause of death in one case.Cyclophosphamide seems to have the same spectrum of activity as othei alkylating agents.Cases of malignant lymphoma resistant to other alkylating agents may be responsive to cyclophosphamide.