RÉSUMÉ
The effects of several preparations of Iscador, a commercially obtainable extract of mistletoe, Viscum album L., on cell proliferation and cell viability was studied. Iscador Quercus was shown to inhibit cell proliferation of: human fibroblast cell lines, mouse tumour cell lines, human carcinoma tumour cell lines and a human lymphoblastic tumour cell line. Iscador Quercus, Iscador Ulnus and Iscador Malus were about equally cytostatic to mouse 3T3 fibroblasts. Iscador Pinus was somewhat less cytostatic. Iscador Quercus had a very direct cytotoxic effect on MOLT4 tumour cells as assessed by trypan blue dye exclusion. The cytostatic and cytotoxic properties of Iscador could be annulled by heating Iscador form 30 min. at 90 "graus"C. Iscador reduced the cloning efficiency of ASG experiments it can be concluded that a small percentage of CHO cells is insensitive to high concentrations of Iscador at short incubation times. The importance of these findings in relation to the cytostatic and cytotoxic compounds possibly present in Iscador is discussed