An aminopropylaminobleomycin represented by the following formula or a salt thereof, which is minimized in side effects such as pulmonary toxicity:[BX]--NH--(CH.sub.2).sub.3 --A--)CH.sub.2).sub.3 --Bwherein[BX] represents the acyl group of bleomycinic acid whose formula differs from that of bleomycin acid by the removal of the hydroxyl group from the carboxyl group of said acid;A represents a group of the general formula ##STR1## wherein R.sub.1 is a lower alkyl or benzyl,R.sub.2 is a lower alkyl or benzyl,R is a lower alkylene, andn is 0 or 1; andB represents a group of the formula ##STR2## wherein (i) R.sub.3 is hydrogen and R.sub.4 is(a) benzyl substituted by one or more halogen atoms, provided that the benzyl is substituted by two halogen atoms when R.sub.1 is lower alkyl,(b) benzyl substituted by cyano, two or more alkoxy groups or two or more benzyloxy groups,(c) lower alkyl substituted by cycloalkyl or anthranyl,(d) phenylethyl substituted by one or more halogen atoms, or(e) diphenylethyl; or(ii) both R.sub.3 and R.sub.4 are benzyl which may be substituted by one or more(a) benzyloxy groups,(b) ring substituted benzyloxy groups in which the ring substituents may be one or more halogen atoms, lower alkoxy groups or benzyloxy groups, or(c) cycloalkylmethoxy groups;and a process for the preparation thereof.