Granulins and polyhedrins from five baculoviruses exhibit similar chemical and physical properties. Although similarities are demonstrated, it has been shown that each of the proteins is different and apparently specific to a given virus. The granulins and polyhedrins exhibit a major polypeptide component of an estimated molecular weight of 28,000. Alkaline protease activity has been detected in each preparation. N-terminal analyses reflect differences between granulins and polyhedrins studied: granulosis virus = Asx, and nuclear polyhedrosis virus = Glx. Two-dimensional high-voltage electrophoresis of highly purified granulin and polyhedrin preparations reveals relatedness as well as differences among the proteins as assessed by electrophoretic migration patterns.