The effects of daptomycin on exponential phase cells of Bacillus megaterium were investigated. Bacteriostasis was observed for concentrations between 1 and 3 micrograms/ml and maximal rate of cell lysis at 10 micrograms/ml. At sublytic concentrations (1.5-3 micrograms/ml), the variations of the pools of UDP-N-acetylglucosamine and UDP-N-acetylmuramyl-pentapeptide, as well as the incorporation of (14C)-N-acetylglucosamine into peptidoglycan were studied. From the results it was concluded that the lethal target of daptomycin could be a metabolic step between glucosamine 6-phosphate and UDP-N-acetylglucosamine.