The defensive secretion of Peripatopsis moseleyi (Onychophora) consists of 84% water and 16% protein and free amino acids. The secretion’s defensive effectiveness is an anti-predator “sticking” action. The secretion is flung out of the oral papillae in liquid state. It is then denaturized by the air and develops increasingly sticky white threads, probably through the development of disulfide bridges from the protein content. The elastic properties of the secretion threads indicate a micellar structure. The defensive secretion contains no volatile organic components or carbohydrates. This was confirmed by gas- liquid chromatography and thin-layer chromatography. After acidic hydrolysis of the secretion the following amino acids were determined quantitatively: aspartic acid, threonine, serine, proline, glutamic acid, glycine, alanine, valine, cysteine, methionine, isoleucine, leucine, tyrosine, phenylalanine, lysine, histidine and arginine. A “rare” amino acid was not identified. Tryptophane was not present (basic secretion hydrolysis). The quantitative determination of free amino acids, based on the total content, showed the following results: glycine (40.9%), glutamic acid (10.8%), aspartic acid (2.65%), lysine (1.3%). This result shows, that the secretion is stored in a watery glycine/glutaminic acid buffer in the oral papillae of Peripatopsis moseleyi. High voltage paper electrophoreses and gel filtration experiments with dextran and agarose gels showed, that the secretion protein consists of, at least, two fractions with different molecular weight.