A comparative analysis of mRNA decay was carried out in Escherichia coli using the wild-type and an isogenic RNase III deletion strain. We have studied the mRNA degradation from the Escherichia coli gene bolA, the Lactococcus lactis biovar diacetylactis citQRP operon and the Desulfovibrio vulgaris Hildenborough gene cyc. As seen by a dramatic stabilization of the specific mRNAs in the mutant strain, RNase III was crucial for the decay process of these three messages. Since RNase III, unlike RNase E, is not essential for bacterial viability we think that there is potential for using RNase III mutant strains to modulate gene expression.