Summary: Six specimens of talc studied by the electron microscope lattice-imaging and diffraction techniques were found to have the triclinic one-layer (1 Tr) structure. Since no evidence of a monoclinic two-layered structure was found in any specimen it is concluded that the 1 Tr structure is the common one for talc, and it may, moreover, be the only one. Extremely fine polysynthetic twinning and single intrinsic stacking faults were found in talc.