Peritrophic matrix (peritrophic membrane or PM) is an important structure in the gut of most insects at some stage in their development. It is composed of chitin, proteins and proteoglycans. Multiple roles for the PM ranging from partitioning of digestive enzymes and food to protection of gut epithelial cells from viral and parasitic invasion have been proposed. While most adult members of Diptera have a Type I PM synthesized in response to a blood meal, the medically and agriculturally important vector insect, tsetse has a sleeve-like Type II PM which is constitutively synthesized by cells in the proventriculus (cardia). Using a differential hybridization approach, we have identified three abundant cDNAs from a proventriculus cDNA library of GLOSSINA MORSITANS MORSITANS: GmPro1, GmPro2 and GmPro3. DNA sequence analysis indicates that GmPro1 and GmPro2 share similarities with the peritrophin-15 family of larval PM proteins, while GmPro3 is a member of the serine protease family. Northern analysis indicates that transcripts for all three cDNAs are preferentially expressed in the proventriculus tissue. The expression profile of these genes in response to the presence of trypanosome indicates that transcription of GmPro1 is increased in the presence of parasites (immune sensitive), while the other two are not affected. Western analysis using antibodies developed against the recombinant GmPro2 shows its primary localization in the gut to be within the peritrophic matrix structure. We discuss the molecular characteristics of these proventriculus specific cDNAs and their products as well as their potential role for vector control studies.