In common with many G protein-coupled receptors, dysfunction in members of the Class B or glucagon-like receptors can elicit a wide spectrum of disease related activities. Consequently, they are potential targets in many different areas of pharmacological research. Unlike the class A or rhodopsin-like receptors, for which at least some structural similarity to bacteriorhodopsin has been detected, absolutely no structural information is available for the Class B G protein-coupled receptors. We present a computational study that exploits the experimental work performed by evolution to indicate residues that are potentially involved in ligand binding in the Class B G protein-coupled receptors. We perform an analysis of mutations that occurred in a correlated fashion between the receptors and their peptidic ligands. The inference that the residues detected in this manner are involved in a direct interaction between the receptor and the ligand is in good agreement with the mutation studies that have already been published.