Dayem‐bridge weak links have been fabricated by sputter etching niobium nitride thin films havingTc's of ∼15 K. These junctions exhibit a negative resistance region extending to 45 mV at 3.2 K, in which are seen self‐induced subharmonic current steps and structure near the energy gap voltage. Temperature dependence of these features and effects of applied microwave radiation are discussed, and possible explanations of the negative resistance region and of the self‐induced step structure are given.