Non ionic thiol-ended surfactants have been prepared either by esterification of thioglycolic acid with poly(ethylene oxide) methyl ether or by anionic coordinated polymerisation of ethylene oxide in the presence of bromo-11-undecanol as transfer agent followed by reaction with thiourea and subsequent hydrolysis. The surfactants have been characterized by H-I NMR, as well as the possible by-products. The transfer constants are in the range 16-19 and decrease with the chain length.