1-β-Hydroxyethylimidazolidine-2-thione was prepared from 1-amino-5-hydroxy-3-azapentane and carbon disulphide. Since its properties differ from those claimed by Sergeyev and Kolychev (7) for this compound prepared from ethylene oxide and thiocyanic acid, its structure was confirmed by conversion to 1-β-hydroxyethyl-2-benzylamino-2-imidazoline. The latter compound was prepared for comparison from the known 1-β-hydroxyethyl-2-nitramino-2-imidazoline.