A modified dislocation unlocking technique is used to measure dislocation locking due to nitrogen implanted into Czochralski silicon. The results show that near-surface dislocations can be locked by implanted nitrogen. The magnitude of the locking measured suggests that nitrogen transport proceeds by a dissociative mechanism, where transport occurs by the splitting of immobile dimers into fast monomers, rather than movement of nitrogen dimers. In other experiments, nitrogen-doped float-zone silicon is investigated using the standard dislocation unlocking technique. The results give an activation energy for effective nitrogen diffusion in silicon of 3.24 +/- 0.25 eV at 500-750 degrees C. Using the assumption that the dislocation locking strength per nitrogen atom is the same as that of oxygen, a value of 200,000 cm(2) s(-1) can be inferred for the effective diffusivity prefactor. If analyzed using the dissociative model, an activation energy of 1.1-1.4 eV is found for nitrogen monomer diffusion, with a diffusivity prefactor of 30 cm(2) s(-1).