A diuretic hormone (DH) was isolated from extracts of heads of Zootermopsis nevadensis, a dampwood termite. The peptide has 46 residues, M(r) = 5,328.2 Da, with the sequence TGAVPSLSIVNPLDVLRQRLLLEIARRRMRQSQDQIQANREMLQTI-NH(2,) showing it to be a CRF-related DH. This peptide increases cyclic AMP production in Malpighian tubules of Manduca sexta. We detected another factor in the head extracts which behaved as a more basic peptide on ion exchange chromatography. The latter factor also stimulated cyclic AMP production in the bioassay, but two large scale attempts to isolate this peptide were unsuccessful. We believe the second peptide is acid labile.