This paper describes the synthesis of oligoribonucleotides by T4 RNA ligase and their identification. The products are a dodecaribonucleotide CpGpGpA32pCpUpCpGpUpCpCpA and a hexadecaribonucleotide ApUpUpC32pCpUpCpGpUpCpCpA, representing the 3'-end nucleotide sequences of the yeast alanine transfer RNA. Particular emphasis was placed on the conditions for the joining reaction, using oligoribonucleotides of defined sequence as the substrates. CpGpGpA32pCpUpCpGpUpCpCpA was synthesized with 32pCpUpCpGpUpCpCpA as the donor, and CpGpGpA as the acceptor in rather low ratio of acceptor to donor. Both the yield and purity of the joining product were above 90%. 32pCpGpGpA32pCpUpCpGpUpCpCpA was used in turn as the donor, and ApUpUpC as the acceptor for further synthesis of the hexadecaribonucleotide ApUpUpC32pCpGpGpA32pCpUpCpGpUpCpCpA with a yield of 60%.