Eleven new polyhydroxysterols (1-11) and eight new saponins (12-19) were isolated from the brine shrimp active fraction of the starfish Certonardoa semiregularis. The structures were determined on the basis of spectral analysis and chemical derivatization. The structural variations of these compounds are due to the hydroxylation pattern of the sterol nucleus, the functionalization of the side chain, or the nature and location of the saccharide moiety. These compounds displayed considerable cytotoxicity against a small panel of human solid tumor cell lines.