Nitration of 4,6-dihydroxypyrimidine in sulphuric acid gave nitroform as the sole product. This behaviour was tentatively explained by the formation of an intermediate, 5,5-dinitro-4,6-dihydroxypyrimidine, that underwent hydrolysis in the nitrating acid to gem-dinitroacetyl formamidine. This compound was further nitrated in the same reaction mixture to trinitroacetylformamidine which finally underwent hydrolytic cleavage to nitroform. It was also demonstrated that gem-dinitroacetyl ureas were able to produce nitroform on nitration. The structures of the proposed trinitroacetylureas were confirmed by the isolation of one of their derivatives.