New cyclic penta or hexapeptides, dichotomins A-E [A: cyclo(-Gly-Thr-Phe-Leu-Tyr-Val-); B: cyclo(-Gly-Thr-Phe-Leu-Tyr-Thr-); C: cyclo(-Gly-Thr-Phe-Leu-Tyr-Ala-); D: cyclo(-Gly-Val-Gly-Phe-Tyr-Ile-); E: cyclo(-Gly-Tyr-Ala-Phe-Ala-)] have been isolated from the roots of Stellaria dichotoma L. var. lanceolata Bge. Their structures were elucidated on the basis of extensive 2D NMR, chemical degradation and X-ray crystallographic analysis. Cyclic peptides are frequently encountered natural products exhibiting a wide variety of biological activities. Despite their importance, surprisingly few studies of higher plants occurring cyclic peptides exist in the literature. As a part of our continuing studies in search of new bioactive cyclic peptides from higher plants, we have already isolated a novel cyclic peptide, named dichotomin A, showing cell growth inhibitory activity, from the roots of Stellaria dichotoma L. var. lanceolata Bge. (Caryophyllaceae), which was used as folk medicines for antifebrile and so on. Continuous fractionation effort of the methanolic extract led to several peptidic compounds, named dichotomins B-E. Here we report a full account of the structure elucidation of dichotomins A-E (1-5) by extensive 2D NMR, chemical degradation and X-ray analysis. The cell growth and cyclooxygenase inhibitory activities were also discussed by using the structures and conformations of dichotomins, analyzed by X-ray and extensive NMR methods