This study on Scandinavian softwood focused on the effects of polysulfide in modified continuous cooking (MCC) and isothermal (ITC) kraft cooking. The polysulfide was assumed to be generated by partial white liquor oxidation. A polysulfide sulfur charge increased the carbohydrate yield. The selectivity regarding pulp viscosity was about the same for pulps produced with and without polysulfide, provided the polysulfide cook was carried out at a 10% higher white liquor sulfidity. The tear strength was lower for the polysulfide pulps at a given kappa number, as expected. Application : polysulfide could be used in a modified kraft cook to low kappa numbers to produce pulp with a higher carbohydrate yield, compensating the yield loss in low kappa pulping.