Three new diterpenes, sugikurojins A-C (1-3) were isolated from the black heartwood of Cryptomeria japonica. The structure of sugikurojin A was deduced to be 19-hydroxy-6,7-dehydroferruginol on the basis of extensive NMR experiments. Sugikurojin B was a dimer of 6,7-dihydroxyferruginol and 6,7-dehydroferruginol with a 6-O-11' linkage. Sugikurojin C was a dimeric ferruginol with 6-O-7' and 7-O-6' linkages. Also obtained in this investigation were the known compounds formosaninol (4), 15 sesquiterpenes (5-19), 16 diterpenes (20-35), three phenylpropanoids (36-38), and a phenolic compound (39).