Litomosoides carinii microfilariae were exsheathed by freezing and thawing, and the sheaths were separated by filtration. Samples of pure sheaths thus obtained were hydrolyzed, methanolyzed or oxidized with nitric acid under pressure at 300 degrees C, respectively, and were analyzed for amino acids, sugars, fatty acids or for metal ions and phosphorus. Almost 75% of the sheath dry weight could thus be accounted for. Amino acids (55 weight %) were the major constituents, and amongst these glutamine and proline (approximately 11% each). The detection of 2% cysteine/cystine indicated the possible presence of disulfide crosslinks. Besides amino acids, approximately 8% of sugars--roughly equimolar amounts of (N-acetyl)galactosamine and uronic acids--1.5% of monovalent cations (Na+ and K+) and 9.5% of phosphate were detected. No appreciable amounts of fatty acids, neutral sugars, neuraminic acid, or (N-acetyl)glucosamine (i.e. no chitin) were found.