Specialized ribosomes, developed by de Boer and co-workers at Genentech, carry a mutation in the anti-Shine-Dalgarno region of 16 S ribosomal RNA, the site of messenger RNA binding. A complementary mutation in the ribosome binding site (the Shine-Dalgarno region) of a particular messenger RNA results in specific and efficient translation of that messenger RNA on the specialized ribosomes. With this system, a fraction of the cell's ribosomes can be dedicated to the translation of a single messenger RNA; the remaining wild-type ribosomes carry out the normal cellular translation processes. Specialized ribosomes have been used for the overproduction of proteins, analysis of the feedback regulation of ribosomal RNA synthesis, and mutational analysis of 16 S ribosomal RNA. Experimental results related to each of these topics are summarized and discussed, and other potential applications are described. In particular, we propose a novel technique for mutational analysis of 23 S ribosomal RNA, the primary RNA constituent of the large ribosomal subunit, using the specialized ribosome approach.