The outgrowth of spores of Bacillus subtilis 168 proceeded normally in temperature-sensitive DNA mutants under restrictive conditions and in the absence of DNA synthesis. Two inhibitors of DNA synthesis, nalidoxic acid and 6-(p-hydroxyphenylazo)-uracil, inhibited spore outgrowth under some nutritional conditions; this inhibition of outgrowth however, though not that of DNA synthesis, could be reversed by glucose. The sensitivity of the outgrowing spores to nalidixic acid and 6-(p-hydroxyphenylazo)-uracil inhbition decreased as a function of outgrowth time. The cells became completely resistant to the inhibitors after 90 min. The development of this resistance occurred also in the absence of DNA synthesis. It was concluded that DNA synthesis is not needed for spore outgrowth, and that outgrowing cells and vegetative cells differ in their sensitivity to these inhibitors.