Iberis amara L (Brassicaceae) is wide-spread in Europe and grows preferably in grain fields, in warm, sunny and dry, mainly loamy and loessial soil which is high in calcium. The plants contain amines, cucurbitacines, flavonoglycosides, and mustard oil glycosides. A fixed combination of the whole, blooming, fresh plant with clear seed formation ( Iberis amara totalis) is used in a phytotherapeutical product (Iberogast). In pharmacological studies both in vitro (e.g., in guinea pig ileum) and in vivo (e.g., in Wistar rats) the fresh plant extract of Iberis amara (IF) exhibited a tonicising effect on the smooth muscles of the stomach and small intestine. In the rat IF produced a dose-dependent antiulcerogenic effect (indomethacin-induced ulcer) comparable to that of cimetidine (reference substance). The stomach acid release and the leucotriene-concentration, increased by indomethacin, were reduced by IF, whereas the prostaglandin E2 content, reduced by indomethacin, was increased. In patients with irritable bowel syndrome as a subtypological symptom associated with diarrhea and in patients with alternating diarrhea and obstipation, clear differences were found between drug and placebo in a multicenter, prospective, double-blind, randomized parallel group comparison. Toxological studies conducted with various cell lines in vitro and in rats and mice have shown that the fresh plant extract of Iberis amara in therapeutical relevant doses has no cytotoxic and no acute toxic action. In mutagenicity investigations there were no indications of genotoxic or mutagenic potential.