We report on the formation of novel RNA molecules in a recombination-like, nonenzymatic reaction proceeding in the complex of partially complementary RNA-oligonucleotides under very simple conditions. Analysis of the isolated products demonstrated that at least 5% of the formed linkages are of the (natural) 3',5'-phosphodiester type. We suggest that similar reactions could contribute to the development of the 'RNA world', but could also proceed in vivo within variously structured RNA or RNA complexes containing loops, bulges, or dangling ends, providing an emergence of novel RNA sequences.