The structures of both low‐ and high‐angle grain boundaries are examined from a dislocation approach, and it is shown that coincidence‐site lattice theory can adequately account for the structure of boundaries of any angle. For simplicity, the structures of symmetric tilt and twist boundaries in simple cubic structures are analyzed. The concepts that are developed, however, are quite general and can be applied to more complex crystal structures. In particular, it is shown that any grain boundary can be considered to arise from some suitable combination of crystal lattice dislocations associated with each one of the two grains comprising the boundary. Although the analysis is done with rigid models, the conclusions reached are independent of any atomic relaxations that occur at the boundary. The results developed from the dislocation approach are compared with those of Bollmann's O‐lattice theory, and it is shown that the relatively complex O‐lattice theory may not be necessary for an understanding of the dislocation structure of grain boundaries. Also, concepts such as the Burgers circuit are rationalized, and it is shown that the defect content described by a given circuit depends directly on its reference lattice whereas the strain fields are related to the relaxations that occur around the defect.