Peptidyl-tRNA hydrolase in Escherichia coli, encoded by pth, is essential for recycling tRNA molecules sequestered as peptidyl-tRNA as a result of pre-mature dissociation from the ribosome during translation. Genes homologous to pth are present in other bacteria, yeast and man, but not in archaea. The homologous gene in Bacillus subtilis, spoVC, was first identified as a gene involved in sporulation. A second copy of spoVC, under the control of the xyl promoter, was integrated into B. subtilis at the amy locus. In this background, interruption of the original gene was possible provided that expression of the copy at the amy locus was induced. When spoVC was interrupted, both vegetative growth and sporulation were dependent on xylose, showing that SpoVC is essential. The role of SpoVC in sporulation is discussed and appears to be consistent with previous hypotheses that a relaxation of translational accuracy may occur during sporulation. The homologous gene in Saccharomyces cerevisiae, yHR189W, has been interrupted in both haploid and diploid strains. The mutant haploid strains remain viable, as do the yHR189W mutant spores obtained by tetrad dis-section, with either glucose or glycerol as carbon source, showing that the yHR189W gene product is dispensable for cell growth and for mitochondrial respiration.