Culture conditions affecting lignin degradation of an unbleached hardwood kraft pulp by Phanerochaete chrysosporium have been examined. Optimum pH and temperature for lignin degradation (about 33%) were 3.5 and 38°C, respectively. Optimum fungal growth was at a pH of 4.5 and a temperature of around 32°C. Addition of exogeneous glucose to the cultures lessened the degradation of pulp carbohydrates. Lignin degradation was stimulated by oxygen atmosphere and non-agitated cultures. Increased surface to volume ratio (decreased culture depth) enhanced lignin degradation (about 56% at a depth of 1.2 cm). Finally, the correlations: pulp yield vs. residual glucose, ligninase activity vs. mycelium, and extent of delignification vs. residual extracellular H2O2 were discussed in light of recent findings of ligninases responsible for ligninolysis.