Oxygenated lanosterol derivatives, which were isolated from Ganoderma lucidum (Polyporaceae) or their derivatives obtained by chemical conversion, were tested for their effect on cholesterol biosynthesis from 24,25-dihydrolanosterol by rat hepatic subcellular 10,000 x g supernatant fraction. The sterol (VI, 40 microM) with 7-oxo and 15 alpha-hydroxy groups potently inhibited the synthesis of cholesterol from [24,25-3H]-24,25-dihydrolanosterol (18 microM).