In this study we compared the cellular concentrations and stability of the mRNA transcribed from the aprE (subtilisin) gene (a gene preferentially expressed in stationary growth phase) with those of a vegetative mRNA, succinate dehydrogenase (SDH) mRNA. The subtilisin transcript was shown to be at least 3 times more stable in early stationary phase than it is 2 hr further into stationary phase. When cells were shifted from maximum expression of the subtilisin transcript in stationary phase to physiological conditions, which allowed for the resumption of vegetative growth, the cellular concentration of the subtilisin mRNA decreased rapidly. We conclude that mRNA degradation is one of the means by which the cellular concentrations of the SDH and subtilisin transcripts are adjusted in response to growth stage.