The by-products which were occured in the synthesis of 5-ethyl-5-phenyl barbituric acid were isolated by column chromatography combined with gas-liquid chromatography and were identified by elemental analysis, ir, nmr and mass spectroscopy ; major by-products were ethyl${alpha}$-phenylbutyrate and ${alpha}$-phenylbutyramide. The alkoxide which was known to be a condensation agent not only accelerated the condensation but also did the decarboxylation. And the entity concenrned with the condensation with diethyl ethylphenylmalonate was not urea but N-monosodium urea.