Compositions for delivering a biologically active drug into a specific site in vivo which comprise microbubble-containing microspheres originating in albumin containing perfluorocarbon. The biologically active drug is preferably at least one member selected from the group consisting of oligonucleotides, antisense oligonucleotides, triple helix-forming oligonucleotides, oligonucleotide probes, nucleotide vectors, virus vectors and plasmids. In using these compositions, the specific site is exposed to ultrasonic wave so that the biologically active drug can be introduced into the specific site.