The position of the substituted bromine in bromination of 1, 3-cyclohexanedione monoenolate with N-bromosuccinimide was investigated. 1, 3-Cyclohexanedione-3-monoenolates, which have two alkyl substituents at their 5-position, were found to be brominated at positions other than 2. From the data obtained in infrared spectra, the stereochemical situations of the bromo substitution were discussed. In this reaction dibromo compounds were obtained as by-products which were not found in a similar reaction for 1, 3-cyclohexanedione monoenolates having no or one aryl substituent at their 5-positions.