Gel electrophoresis was used to determine the number and size of the subunits present in the protein crystals from 16 strains of B. thuringiensis. The calculated MW fell into 3 major categories whose crystals exhibited the following protein banding patterns: type I, high MW only (140,000-160,000); type II, both high MW and medium MW (60,000 and 150,000); and type III, low MW only (40,000-50,000). Interestingly, the type I and type II crystals were the expected bipyramidal diamonds whereas the type III crystals possessed a previously unreported tetrahedral shape.