Oligomers of vinyl esters, preferably of vinyl acetate, are provided in which the molecules contain a single terminal sulfonate group, thereby making these products useful as surface-active agents. These oligomers can be converted by hydrolysis to sulfonate-terminated vinyl alcohol oligomer which is also a surface-active agent. The number average molecular weight of the vinyl ester oligomer is not over 17,000 and not over 7,500 for the vinyl alcohol oligomer. These products are made by polymerizing the vinyl ester in the presence of a bisulfite chain transfer agent in water, preferably with a cosolvent such as methanol. The vinyl ester is delay fed to the polymerization, molecular weight is controlled with the bisulfite, and the system is maintained in a virtual single phase with any organic phase present swollen with water or water and cosolvent.