Having established the hypothesis that the carcinostatic effect of Iscador described in the literature and ascertained by own observations should also show in the treatment of carcinoma of the ovary, we compiled all respective cases treated since November 1969 in the Gynecological Ward of the Gemeinnütziges Gemeinschaftskrankenhaus Herdecke. The collective consisted of 25 patients with primary neoplasms of the ovary who received post-operative treatment with Iscador. The average age was 50.96 years. 20 women were in the advanced stages III and IV according to FIGO. Five-year survival rates were 100% in stages I and II, 23% in stage III and 0% in stage IV. After establishing best possible congruence, our group of patients was compared with a collective of 22 women with neoplasms of the ovary who had received post-operative treatment with Cytoval. Inspite of less favorable prognostic indicators for the Iscador patients, the latter reached an average survival rate of 16.2 months as compared to 5.2 months in the group treated with Cytoval (ratio 3.1:1). The survival period of Iscador patients in stage III was 4.2 times longer, in stage IV 1.6 times longer than that of the Cytoval patients. The difference is statistically significant (alpha less than 0.018). A comparison of the results of the two collectives shows that Iscador a special preparation of viscum album, is a useful and effective treatment of carcinoma of the ovary, particularly since it usually does not cause serious and undesired side effects. Thus the original working hypothesis was confirmed.