This paper describes a high resolution electron microscopy study of thorotrast in human tissues. Specimens were prepared from autopsied and biopsied liver samples, and from a surgically removed Thorotrast granuloma taken from patients. Lattice images were taken by a high-magnification X 380,000 at 200KV with an analytical electron microscope. The lattice distance of Thorotrast was 3.2A, which is identical with the lattice distance of Th02 (1,1,1) face. Direct imaging of the crystal lattice gives useful information about the structure and relative orientations of microcrystallites in tissues.