The proteinase inhibitors (PIs) active against bovine pancreatic trypsin, chymotrypsin, and insect midgut trypsin-like proteinases were found in the seeds of 14 cultivars and eight wild types of pigeonpea, Cajanus cajan L.. The inhibitory activity of PIs against trypsin and chymotrypsin, as well as their activity profile on gelatin-polyacrylamide gel electrophoresis (PAGE) were identical among the various cultivars. In contrast to cultivars, the wild types showed differences in inhibitory activity of PIs and their activity profile on gelatin-PAGE. The PIs from all cultivars and few wild types showed 10- to 50-fold higher activity against midgut trypsin-like proteinases of Achaea Janata (L.) (Lepidoptera: Noctuidae), compared with bovine pancreatic trypsin. However, the PIs from both cultivars and wild types showed three- to nine-fold less activity against Spodoptera litura (F.) (Lepidoptera: Noctuidae) midgut trypsin-like proteinases, compared with bovine pancreatic trypsin. This inhibitory potential of PIs from cultivars and wild types, toward midgut trypsin-like proteinases from A. Janata was further evident by the strong activity profile visualized on gelatin-PAGE. These results further suggest that the inhibitory potential of PIs from pigeonpea cultivars and wild types could be exploited in management of nonhost insects.