Terpenoids, 1, 2 and 3, which selectively inhibit eukaryotic DNA polymerase activities, were isolated from the fruiting body of a basidiomycete, Ganoderma lucidum, and their structures were determined by spectroscopic analyses. New terpenes, lucidenic acid O (1) and lucidenic lactone (2), prevented not only the activities of calf DNA polymerase α and rat DNA polymerase β, but also these of human immunodeficiency virus type 1 reverse transcriptase. Cerevisterol (3), which was reported to be a cytotoxic steroid, inhibited only the activity of DNA polymerase α. Although these compounds did not influence the activities of prokaryotic DNA polymerases and other DNA metabolic enzymes such as T7 RNA polymerase and deoxyribonuclease I.