Since 1971 the efficacy of a combination chemotherapy, which included the nitrosoalkylurea derivative nitrosomethylurea, was tested in three clinical trials. The combination of vincristine (VCR), nitrosomethylurea (NMM) and actinomycin-D (Act.-D) showed an activity of 34.9% (10.9% CR + 24% PR) with a duration of remission from 2 to 30 months in 92 patients. The comparison of the combination VCR, NMM, Act.-D (group 1 = 44 pat.), VCR, NMM, Act.-D, DTIC (group 2 = 46 pat.) and VCR, Act.-D, CCNU, DTIC (group 3 = 48 pat.) showed an efficacy (CR + PR) of 29.6%; 28.3% and 18.8%. The duration of remission within all three groups is significantly longer in patients with a CR. In the first and second group the survival after 12, 18 and 24 months is significantly better than in the third group. The median survival time of patients reaching CR is in the first and second group (30.4 and 28.7 months) significantly better than in the third group (20.5 months). The comparison of a DTIC-monotherapy (group 1 = 56 pat.) and the combination VCR, NMM, Act.-D. (group 2 = 58 pat.) showed 7.1% CR and 16.0% PR, and 13.7% CR and 10.4% PR respectively. A cross over, when a progression occurred, was ineffective; survival time being 6.9 and 6.5 months did not differ.