Described is a process for producing aqueous solutions of vinyllactam polymers and solids obtainable therefrom by drying, especially polyvinylpyrrolidone, said process comprising using one or more sulfur components selected from the group consisting of sulfur dioxide, sulfurous acid and one or more salts of sulfurous acid, to reduce residual monomer. Also described are vinyllactam polymers obtainable by the process which have good stability in storage, the use of these vinyllactam polymers, and articles of manufacture and preparations comprising these vinyllactam polymers or obtained by use thereof.