Pre-treatment of wood chips with white-rot fungi (i.e. biopulping) has previously been shown to decrease the energy consumption in mechanical pulping. In this study, promising novel fungal isolates were found for biopulping of Norway spruce (Picea abies). Three hundred fungal isolates were evaluated by agar plate tests. According to the results, 86 isolates were chosen to a wood block decay test. The characteristics of the fungal attack and the wood decay were studied and chemical analyses of cellulose, lignin, and hemicelluloses in the residual wood were performed. The results showed both interspecies and intraspecies variations in the degradation patterns of these compounds. After a 10-week incubation period, 17 of the novel white-rot strains showed selective lignin degrading ability, based on the chemical analyses. Some of these lignin-selective strains also grew well even at +37 degreesC. The selectivity value, i.e. the lignin/cellulose loss ratio, was higher for I I of the studied strains compared to the widely studied Ceriporiopsis subvermispora. In this study, Physisporinus rivulosus T241i was shown to be a superior novel isolate for softwood biopulping applications based on its growth characteristics through a wide temperature range and its selectivity towards lignin. (C) 2003 Elsevier Inc. All rights reserved.