Fourteen sesquiterpene and norsesquiterpene derivatives, comprising six different carbon skeletons, were isolated from Sanicula lamelligera. Saniculamoid A1 (1a) is an oxidation product of saniculamoid A (1), created by the transition of a formyl group to a carboxylic acid group after a period of storage in air. The known compounds 5-14 were identified in Sanicula plants for the first time. The compounds were evaluated for their anti-HIV-1, cytostatic, and nitric-oxide-production-inhibiting activities using in vitro cellular assays. The results showed that 1,5-naphthalenediol inhibited nitric oxide production in lipopolysaccharide-stimulated RAW 264.7 cells with an IC₅₀ value of 28.1 μM and was active toward five cancer cell lines with IC₅₀ values in the 31.1-41.6 μM range.