This research examined the ability of two biopulping fungi, Ceriporiopsis subvermispora and Phanerochaete chrysosporium, to lower the resin content of wood chips, and the ability of a commercial depitching fungus, Ophiostoma piliferum, to biopulp. Biopulping is defined as the pretreatment of wood chips with lignin-degrading fungi for mechanical pulping. The study also examined the effect on sulfite pulping of the fungal pretreatments. Ceriporiopsis and Ophiostoma lowered the resin content of loblolly pine (2.55-2.64%) by 18-27% in 2 weeks and 33-35% in 4 weeks (Phanerochaete was not studied), and all three fungi lowered the resin content of spruce wood from 1.2% to 0.8-0.9% in 2 weeks. In a biopulping study, pretreatment of pine wood chips for 4 weeks with Ceriporiopsis lowered the refining energy requirement by 30%, improved certain strength properties, and lowered brightness and light scattering coefficient, in comparison to sterile control chips. By contrast, Ophiostoma had no effect on energy requirements, or on strength and optical properties. Pretreatment of spruce chips with the two biopulping fungi, but not with Ophiostoma, led to lower kappa numbers on sulfite cooking. Tensile index of paper from the sulfite-pulped chips was increased slightly by Ophiostoma and unchanged by the biopulping fungi. Tear index was increased slightly by Ceriporiopsis, decreased slightly by Phanerochaete, and not changed by Ophiostoma.