Effects of the SH inhibitor sodium iodoacetate, alone and with adjuncts menadiol diphosphate, sodium malonate, sodium fluoride and heparin, on incorporation of tryptophane-3 H into nonhistone chromosomal proteins of HeLa cells were examined. The drugs block incorporation of tryptophane-3 H into nonhistone chromosomal proteins far more than incorporation of leucine-3 H into total cellular proteins. Drug effects on thymidine phosphorylation and DNA synthesis in HeLa cells exceed corresponding effects on fibroblasts from normal healing wounds.