The fission yeast Schizosaccharomyces pombe contains in the haploid genome one copy of the gene (designated rrkl) for the RNA components of RNase P. Gene disruption in diploid cells of one copy of rrkl resulted in a moderate reduction of the level of cellular RNase P activity. Haploidization by meiosis demonstrated that rrkl is required for cell growth. Thus, the RNA components of S. pombe RNase P are essential in vivo. This is similar to the situation in Escherichia coli.