The structures of aclacinomycins A and B and 19 analogues were determined by a combination of chemical conversions and degradations and spectral interpretations.In the preceding papers1~4) we have reported Streptomyces galilaeus MA144-M1to produce new antitumor anthracycline antibiotics aclacinomycins A and B, and 19 analogues. These 21 compounds can be devided into two groups by color; the first group consists of yellow-colored pigments, named aclacinomycins, having aklavinone as the aglycone and the second is red-colored group consisting of 7 components assigned to cinerubin groups5,6)having e-pyrromycinone as the aglycone.This paper describes the structural determinations of the aclacinomycins and some chemical and enzymatic conversions.