Several methodical approaches (negative staining, filtration by rotation, modeling, optic diffraction, and filtration of images) were used to study the structure of ther internal capsid of rotavirus and the structure and mutual arrangement of capsomers comprising it. The internal capsid of rotaviruses was shown to be constructed as a skew icosadeltahedron (left) with T-13 and to consist of 12 pentamers and 120 hexamers. The structural units (a total of 780) comprising capsomers are organized into trimers, each trimer participating in the formation of three adjacent capsomers, while each of the structural units is a part of only one capsomer.