These neuropeptides are the first members of the insect kinin-family isolated from the American cockroach. Their occurrence in the retrocerebral complex suggests a physiological role as a neurohormone. The C-terminal sequence Phe-X-Ser-Trp-Gly-NH2 characterized the peptides as members of the insect kinin family. Data suggest a possible involvement of insect kinins in water-balance by regulating the osmoregulation. These peptides have length from 6 to 14 amino acids.