Two bioactive cyanoglycosides, rhodiocyanosides A and B, and two oligoglycosides, rhodioflavonoside [gossypetin 7-O-beta-D-glucopyranosyl(1-->3)-alpha-L-rhamnopyranoside] and rhodiooctanoside [octyl alpha-L-arabinopyranosyl(1-->6) beta- D-glucopyranoside), were isolated from the Chinese natural medicine "Si Lie Hong Jing Tian" (Shiretsukoukeiten in Japanese), the underground part of Rhodiola quadrifida (Pall.) Fisch. et Mey., together with four known compounds: rhodioloside, n-hexyl beta-D-glucopyranoside, gossypetin 7-O-alpha-L-rhamnopyranoside, and tricetin. The chemical structures of new glycosides were determined on the basis of chemical and physicochemical evidence. Rhodiocyanosides A and B exhibited inhibitory activity on the histamine release from rat peritoneal exudate cells sensitized with anti-2,4-dinitrophenyl IgE. Additionally, rhodiocyanoside A, the major constituent of this natural medicine, was also found to show antiallergic activity in a passive cutaneous anaphylaxis test in rat.