Although glycerol is not taken up via the phosphotransferase system (PTS) in Bacillus subtilis, some mutations that affect the general components of the PTS impair the ability of cells to grow on glycerol. Five revertants of a pb deletion mutant that grow on glycerol were analysed. They were shown to carry mutations in the glycerol kinase gene. These are missense mutations located in parts of the g/pK gene that could encode regions important for the activity of glycerol kinase. The results strongly suggest that the main effect of the PTS on glycerol utilization in B. subtilss is mediated via glycerol kinase.