Previous studies demonstrated that acriflavine treatment of early log phase cells ofBacillus subtilisproduced both stable oligosporogenic and asporogenic mutants in high yield. More recently it has been demonstrated that high numbers of oligosporogenic mutants, believed to be defective for a regulatory gene, were found consistently after acriflavine addition. The asporogenic mutants were found on only a few occasions at approximately 19 hours after the addition of acriflavine. Results did not imply that acriflavine selected out either type of mutant. Exposure of late log and stationary phase cells to acriflavine was not effective in producing sporulation mutants. However, if these cells grown to the late growth phase are irradiated with specific doses of ultraviolet light and then treated with acriflavine, high numbers of oligosporogenic mutants appeared. The acriflavine-induced Sp−mutants were not found to be auxotrophic for amino acids or resistant to acriflavine. They had no detectable respiratory deficiencies and produced the protease and bacteriocin associated with the early stages of sporogenesis.