Two new cyclolanostane diglycosides, cimifoetiside A (1) and cimifoetiside B (2), were isolated from an 80% ethanolic extract of the aerial part of Cimicifuga foetida L. (Ranuculaceae). Using spectral data and chemical analysis, the structures of 1 and 2 were identified as (23R, 24S) cimicigenol 3-O-beta-D-glucopyranosyl-(1''-->3')-beta-D-xylopyranoside and (23R, 24S) cimicigenol 3-O-beta-D-glucopyranosyl-(1''-->2')-beta-D-xylopyranoside, respectively. The in vitro immunosuppressive effects of the two new compounds 1 and 2, as well as four other known cyclolanostane saponins 3-6 on T cells were evaluated. All the agents tested effectively inhibited the proliferation of murine splenocytes induced by Concanavalin A (ConA), with IC(50) values ranging from 12.7 nM to 33.3 nM.