AbstractModification of chemithermomechanical pulp (CTMP) by fungal treatment was investigated. Eucalyptus CTMP was treated with three different types of white-rot fungi, namely, Phanerochaete chrysosporium (P.c-1767), Trametes hirsute 19-6 (T.h-19-6), and Trametes hirsute19-6w (T.h-19-6w), under a stationary culture condition. Pulp total weight loss, lignin loss, and cellulose loss were determined to compare the different enzymes secreted by the three fungal strains. Pulp physical strengths, optical properties, and bleachability after the fungal treatment were investigated to compare the effect of fungal treatment on the pulp quality improvement. The results show that lignin reduction by both T.h-19-6 and T.h-19-6 (w) was about twice as much as that by P.c-1767. However, the selectivity of T.h-19-6 (w) towards lignin over cellulose was only 0.82, while that of T.h-19-6 was as high as 4.43. After T.h-19-6 treatment, pulp tensile, tear, and internal bonding strength increased by about 27%, 38%, and 40%, respectively.