IT is now generally accepted that 16S and 23S ribosomal RNA play important roles in the decoding and peptidyl transferase activities of ribosomes^1,2. Despite their complex structures and numerous associated proteins it is possible that small domains of these rRNAs can fold and function autonomously, particularly those that appear devoid of protein interactions³. One candidate for such a domain is the decoding region, located near the 3′ end of 16S rRNA (Fig. la, b). Consistent with this hypothesis, aminoglycoside antibiotics that interact with the decoding region in 30S subunits interact with other RNAs in the absence of proteins^4–7. In addition, certain activities of self-splicing introns, at least superficially, resemble translational decoding^8,9. We report here that an oligo-ribonucleotide analogue of the decoding region interacts with both antibiotic and RNA ligands of the 30S subunit in a manner that correlates with normal subunit function. The activities of the decoding region analogue suggest that the intimidating structural complexity of the ribosome can be, to some degree, circumvented.