Dehydroabietic acid (DHA) (1) is one of the main compounds in Scots pine wood responsible for aquatic and microbial toxicity. The degradation of 1 by Trametes versicolor and Phlebiopsis gigantea in liquid stationary cultures was followed by HPLC-DAD-ELSD. Both fungi rapidly degraded DHA relative to a control. More breakdown products were observed for T. versicolor than for P. gigantea. After 13 days, four compounds were identified by means of spectroscopic methods in P. gigantea cultures: 1beta-hydroxy-DHA (2), 1beta,7alpha-dihydroxy-DHA (3), 1beta,16-dihydroxy-DHA (5), and tentatively 1beta-hydroxy-7-oxo-DHA (4). In T. versicolor cultures, 1beta,16-dihydroxy-DHA (5), 7beta,16-dihydroxy-DHA (6), 1beta,7beta,16-trihydroxy-DHA (7), 1beta,16-dihydroxy-7-oxo-DHA (8), 1beta,15-dihydroxy-DHA (9), and 1beta,7alpha,16-trihydroxy-DHA (10) were identified after 9 days of incubation. Thus the biotransformation of 1 by the two fungi was different, with only 5 being produced by both strains. Compounds 3, 7, 8, and 10 are reported for the first time as natural products.