Silver chloride tabular grains with {100} faces on the surface (hereinafter referred as {100} tabular grain) were prepared by introducing a small amount of silver bromide at their nucleation stage. Their dislocation structure was observed by low-temperature transmission electron microscopy (LTEM) in order to study the mechanism of their anisotropic growth. The results of the observations were as follows: First, a nucleus was observed at one of the corners of almost every {100} tabular grain. Second, two dislocations extended from a nucleus trace in the <310> directions. Third, a {100} tabular grain grew anisotropically from the nucleus only in the two directions to which these two dislocations extended. Fourth, the dislocations thus observed in {100} tabular grains were identified as screw dislocations. We conclude that anisotropic growth of {100} tabular grains is caused by screw dislocations.