Lysophosphatidylcholine (LPC) was found to cause autolysis of Bacillus subtilis 168 cells growing logarithmically at concentrations higher than 20 mu M, by inducing the activity of autolytic enzymes. The lytic activity depended upon the carbon-chain length of the acyl moiety in the LPC molecule, being most effective with palmitoyl LPC. Lysophosphatidylethanolamine also caused cell lysis but to a lesser extent, whereas lysophosphatidylglycerol did not. LPC stimulated cell autolysis in TRIS-KCl buffer and potassium phosphate buffer but was ineffective in distilled water. LPC had no influence on the activity in vitro of partially purified autolytic enzymes.