Distamycin A is a potent inhibitor of transcription and an efficient inhibitor of cellular proliferation. It is produced by the strain of Streptomyces distallicus NCIB 8936. It has the activity against gram-positive bacterium, mycobacterium, dermatophyte and Trichophyte. It has inhibitory effects on solid tumors such as Epstein-Barr ascites carcinoma, sarcoma 180, Walker 258, oberling-Guerin osteoma, and also inhibits vaccinosis virus, herpes simplex virus, adenovirus, and mouse hepatitis virus in cell culture.