Antimicrobial activity of six derivatives and products of chemical modification of antistaphylococcal antibiotic Batumin and one natural analog of this antibiotic formed by the strain-producer has been investigated. Not a single substance, which could exceed Batumin or be equal to it as to activity and selectivity in respect of staphylococci was detected among the studied compounds. It was shown that a unique antimicrobial effect of Batumin was determined by several peculiarities of its molecule: presence of double bonds, group--CONH2, as well as carboxyl and hydroxyl groups. The substitution or modification of each of these groups decreased activity against staphylococci and qualitatively changed antimicrobial spectrum of the antibiotic.