New 3-nitropyrazole compounds of the formula: ##STR1## wherein R.sub.1 is lower alkyl;R.sub.2 is hydrogen or lower alkyl;R.sub.3 is cyano, carboxyl or lower alkoxycarbonyl or the radical --CO-NR.sub.4 R.sub.5, in whichR.sub.4 is hydrogen or hydroxyl, carbamoyl, alkylcarbamoyl, dialkylcarbamoyl, thiocarbamoyl, ureido, thioureido, hydroxyphenyl, picolyl or is a lower alkyl, alkenyl or cycloalkyl radical substituted, if desired, by a cyano, hydroxyl, pyrrolidino, piperidino, amino, lower alkylamino, lower dialkylamino or lower acylamino substituent andR.sub.5 is a hydrogen atom or a lower alkyl radical orR.sub.4 and R.sub.5 together represent a lower alkylene bridge;And the pharmacologically compatible salts thereof are outstandingly effective as anti-microbial agents, particularly systemically and in the urinary tract.