We very briefly describe the main ingredients, including the latest modifications, of the ``HNV'' model for one pion production in neutrino nucleon reactions. We present results for total cross sections as well as pion angular distributions with respect to the pion polar angles measured in the pion-nucleon center of mass. The latter show that the approximation of taking an isotropic distribution, as done in some Monte Carlo generators, is not supported by microscopic calculations. With the corresponding medium effects taken into account, the model is applied to one pion production in nuclei for which we show some preliminary results.