The penetration and transformation of sodium nitrite after injection into pork Longissimus dorsi muscle were examined. In the experimental conditions the injection resulted in distribution of the brine mainly lengthwise the muscle fibres. Equalization of concentrations was found to occur at various rate lengthwise and across the muscle fibres. A higher diffusion rate was noticed across the muscle fibres. Diffusion coefficients in that direction attained three times higher value than those in the direction being in accordance with muscle fibres configuration. Specific paraboidal distribution of nitrite/(nitrate + nitrite) ratio in the diffusion zone of meat during curing process, which reflects the degree of nitrite oxidation to nitrate in the autoredoxidation process, were caused by the presence of nitrates in meat before curing brine injection.