The antibacterial activity of several new 5-aminoorotic acid derivatives considered as possible competitors of orotate towards dihydroorotase has been investigated. Products with a bromacetamido substitution demonstrated antibacterial properties. However, the paradoxical behavior of some compounds in synthetic media, opposed to the expected results obtained with an E. coli strain lacking dehydroorotic dehydrogenase, did not allow us to draw conclusions on their mechanism of action.