Glyoxylic acid 2-benzylsemicarbazone derivatives, chlorinated in the aromatic nucleus (Ia-Id) were prepared either by reaction of glyoxylic acid semicarbazone with the corresponding benzyl chlorides or by treatment of benzylidene semicarbazide with substituted benzyl chlorides and reaction of the formed semicarbazides IIIa-IIId with glyoxylic acid. The semicarbazones Ia-Id were cyclized by heating with sodium hydroxide in ethylene glycol to give the corresponding 1-benzyl-6-azauracils IIa-IId.