The aggregation of poly(rA)-wrapped single-walled carbon. nanotubes (SWNTs) induced by hybridization of the adsorbed polymer with free poly(rU) has been studied by differential UV absorption spectroscopy, NIR luminescence, and AFM. After the addition of poly(rU) into a poly(rA):SWNTs suspension, the double-stranded poky(rA)poly(rU) was formed, which is evident from the characteristic S-like form of the melting curve for the polymer created. Hybridization of free poly(rU) with two complementary poly(M), one of which was adsorbed to different individual nanotubes, links them together and causes the appearance of aggregates. The aggregation of nanotubes is accompanied with light scattering and can be monitored in an AFM image after the deposition of the suspension on a mica substrate. Molecular dynamic simulation demonstrates a possible structure of the SWNTs aggregate.