A new antibiotic, ayamycin A₂, has shown antitumor activity against HeLa cells in vitro and Ehlrich ascites carcinoma in vivo^1,2).

About 20 streptomyces antibiotics have the quinoid structure and several of this group are known to have anti-tumor activity such as cinerubin³⁾, luteomycin⁴⁾, mitomycin C⁵⁾, and ractinomycin A⁶⁾.

Since ayamycin A₂ also belongs to this group, the present study was made to test its effectiveness on a number of experimental animal tumor systems. The tumor spectrum employed consisted of 30 solid tumors, 2 ascites tumors and 1 virus leukemia.