"Viscum album" extract, iscador, was found to reduce the leukocytopenia produced by radiation and cyclophosphamide treatment in animals. Weight loss due to radiation was considerably reduced by "Viscum album" extract whereas weight loss due to cyclophosphamide was not altered. Hemoglobin levels also were not affected by "Viscum album" extract administration. The results indicated that treatment with "Viscum album" extract reduces lymphocytopenia and hence could be used along with chemotherapy and radiation therapy.