From the latex of Jatropha gossypifolia L. (Euphorbiaceae) a novel cyclic heptapeptide was isolated, which we named cyclogossine A. A combination of amino acid analysis, FAB mass spectrometry, and two dimensional 1H-NMR spectroscopy (TOCSY and ROESY) was used to determine the primary structure. The compound was found to contain one glycine, one alanine, one valine, two leucine, one threonine, and one tryptophan residue; its amino acid sequence is: Leu 1 - Ala 2 - Thr 3 - Trp 4 - Leu 5 - Gly 6 - Val 7. The absolute configurations of the amino acids were determined by chiral gas chromatography; all have the L-configuration.