Effects of some organic acids and monoterpenes on production of beta-thujaplicin were studied in Cupressus lusitanica suspension cultures. The fungal elicitor-induced biosynthesis of beta-thujaplicin was promoted by the feedings of malate, pyruvate, fumarate, succinate, and acetate. These results suggest some relationships between acetate/pyruvate metabolism and beta-thujaplicin biosynthesis, or between tricarboxylic acid cycle and beta-thujaplicin biosynthesis. Feedings of C. lusitanica suspension cultures with some monoterpenes inhibited elicitor-triggered beta-thujaplicin biosynthesis, but 2-carene and terpinyl acetate feedings significantly improved the beta-thujaplicin production of C. lusitanica suspension cultures. These results indicate a possible involvement of terpinyl acetate and 2-carene in beta-thujaplicin biosynthesis, as well as potential uses of these monoterpenes in large-scale beta-thujaplicin production.