Complete amino acid sequences have been determined for six larval-pupal cuticular proteins from Tenebrio molitor. The sequenced proteins are major components in both larval and pupal cuticle, and both basic and slightly acidic proteins are represented. The proteins show pronounced similarities to some of the proteins sequenced from other insect cuticles. Three slightly acidic larval-pupal Tenebrio cuticular proteins contain a 66-residue central, hydrophilic region, resembling regions in cuticular proteins from insect species of four different orders (Coleoptera, Diptera, Lepidoptera and Orthoptera), and three basic proteins from larval-pupal Tenebrio cuticle have a 51-residue hydrophilic region in common with two proteins from cuticle of pharate adult locusts (Locusta migratoria). The Tenebrio larval-pupal cuticular proteins are also similar to locust adult cuticular proteins, by frequent occurrence of the short sequence motif Ala-Ala-Pro-Ala/Val. The pronounced sequence similarities between cuticular proteins from different insect orders indicate that the conserved regions are functionally important.