Two new cyclic peptides, dichotomins F (1) and G (2), have been isolated from the roots of Stellaria dichotoma L. var. lanceolata Bge., and the structures were elucidated by chemical degradation, ESIMS-MS, and extensive 2D NMR methods.Recently, much attention has been devoted to cyclic peptides because these interesting natural products exhibit a wide variety of essential biological functions. Many cyclic peptides with unique structures and interesting pharmacological activities have been isolated from marine and micro organisms,2 but only a few examples have been reported from higher plants.1As part of our continuing investigation of new biologically active cyclic peptides from higher plants, we have focused our attention on the isolation of new cyclic peptides from the Caryophyllaceae plants.3 Among them, we have previously isolated new cyclic peptides dichotomins A-E from n-BuOH-soluble fraction of the roots of Stellaria dichotoma L. var. lanceolata Bge., which was used in folk medicine as an antifebrile.4 Some dichotomins showed cytotoxic activity and/or cyclooxygenase inhibitory activity. By the guidance of this assay, further purification of the n-BuOH-soluble fraction resulted in the isolation of two new cyclic peptides, named dichotomins F (1) and G (2). Here, we report a full account of the structure elucidation of dichotomins F and G by chemical degradation, ESIMS-MS and extensive 2D NMR methods; their cyclooxygenase inhibitor activities are also described.