Tenebrio molitor is a pest causing economic loss to the stored product industry. The digestive physiology of T. molitor was studied to develop new control methods, such as proteinase inhibitors, that target digestion in coleopteran pests. T. molitor larvae utilize a complex of proteinases for digestion, including spatially expressed serine and cysteine proteinases. This proteinase complexity in the midgut renders T. molitor a good model to evaluate the regulatory mechanisms of these proteinases in response to dietary inhibitors. T. molitor larval digestive proteinases and the genes encoding them have been characterized. cDNA libraries from the anterior and posterior midgut were constructed. In the sequence analysis of 384 randomly picked clones, more than 20 proteinase sequences that share homology to known insect proteinases in GenBank were detected. The cDNA clones were differentially expressed in the anterior and posterior midgut. Select sequences representing major digestive proteinases were used to design probes to quantify and compare expression. Northern blot analysis and qPCR were used to determine gene expression under different conditions. These results provide information about the regulation of digestive proteinases in coleopteran pests.