The effect of nitridation at 1 000 degrees C in ammonia on porous silicon photoluminescence was studied. These investigations correlated the composition, the paramagnetic defects and the photoluminescence intensity. The composition of the porous layers was determined using nuclear microanalysis and Fourier transform infrared spectroscopy at 8 K. The paramagnetic defects were assessed by electron paramagnetic resonance. The results show that the hydrogen is removed from the SiHx species during the nitridation and that only nitrogen is incorporated in the layer, in the absence of hydrogen coming from ammonia. The paramagnetic defect concentration which increases at first due to the removal of hydrogen, decreases during further nitridation. The photoluminescence intensity is strongly correlated with the defect concentration This passivation which is presently under studies is more stable than the passivation by hydrogen. Annealing at 600 degrees C does not lead to any increase of defect concentration.