Fronds of the fern Microsorum scolopendria are widely used in traditional medicine in the Society Islands. They were investigated for the presence of ecdysteroids, which might be responsible for at least some of their medicinal properties. M. scolopendria represents an excellent source of ecdysone (0.16% of dry weight) and 20-hydroxyexdysone (0.20%), and also contains significant amount (0.01-0.02%) of makisterones A and C, inokosterone and amarasterone A, together with lower amounts of poststerone and of a compound tentatively identified as 24,28-diepi-cyasterone. During this study, three new minor phytoecdysteroids, namely 20-deoxymakisterone A, a 25(?)-epimer of amarasterone A and 25-deoxyecdysone 22-glucoside were also isolated by a combination of normal- and reversed-phase HPLC and subsequently identified by NMR.