3-Bromo-7-nitroindazole is a more potent inhibitor of nNOS than 7-nitroindazole in vitro, but unlike 7-nitroindazole, it is also potent against iNOS. The IC₅₀ values for inhibition of rat nNOS, bovine eNOS, and rat iNOS are 0.17, 0.86, and 0.29 µM, respectively.