Recent interest in the use of of adriamycin-DNA complex as an approach to improve the therapeutic effectiveness and to reduce toxicity of adriamycin for cancer chemotherapy requires an in depth understanding of the physicochemical and biochemical properties of such complexes. The interactions of adriamycin with single strand polydeoxyribonucleotides, double stranded DNA and double strand ribodeoxyribopolynucleotide hybrids were investigated. Association constants (Kapp) of adriamycin and polynucleotides were obtained. These data showed that the inherent variable in such a complex lies in the composition of the polynucleotides. Alternate deoxyguanylate (dG)-deoxycytidylate (dC) sequence binds 7-fold better than alternate deoxyadenylate (dA)-deoxythymidylate (dT) sequence. Comparative studies of the hydrolysis of DNA duplexes by DNases I and II with and without adriamycin were also done. The rate of hydrolysis decreased in the order poly(dA-dT) > calf thymus DNA .mchgt. poly(dG-dC) > poly(dA).cntdot.poly(dT) > poly(dG).cntdot.poly(dC) for DNase I and poly(dA-dT) > calf thymus DNA > poly(dG-dC) > poly(dA).cntdot.poly(dT) .mchgt. poly(dG).cntdot.poly(dC) for DNase II. Intercalation of adriamycin to deoxyribopolynucleotide duplex resulted in inhibition of DNase II 2-3 times more than that of DNase I. Intercalation of adriamycin to homodeoxypolynucleotide duplex poly(dA).cntdot.poly(dT) and poly(dG).cntdot.poly(dC) enhanced DNase I hydrolysis. If DNase I activity could be related to serum DNase and DNase II related to tumor lysosomal DNase as in the endocytosis mechanism proposed by Troulet et al., the best adriamycin carrier suggested by this investigation could be poly(dA).cntdot.poly(dT) and poly(dG-dC). Adriamycin-RNA-DNA hybrid could be of interest as an antiviral agent by a similar release mechanism via RNase H, an enzyme associated with viral reverse transcriptase.