The triterpenoid structure is a promising motif for the molecular design of DNA polymerase inhibitors.(1) In this study, 2-(cholesteryloxy)acetic acid (3), 2-(cholestanyl)acetic acid (7), and 2-(stigmasteryl)acetic acid (11) were found to selectively affect only DNA polymerase alpha (pol.alpha). The presence of a carboxyl group at position 28 appears to be essential for the inhibition of the pol.alpha activity. With pol.alpha, these compounds acted by competing with the template-primer DNA and noncompetitively with the substrate.