In order to obtain reliable structural models of molecular arrangements in low-dimensional dye aggregates, crystal structures of nineteen cyanines, four merocyanines, eight styryls, and six TCNQ salts of cyanines have been investigated by X-ray crystallography. In most of the crystals the dye molecules stack face-to-face to form columns or one-dimensional arrays; they were classified into five distinctive types according mainly to the disposition of inversion center that relates the adjacent dye molecules; this confines the magnitudes of the columnar and the nearest-neighbor slip-angles. The columns assemble together to form layer-like or two-dimensional arrangements which resemble those so far proposed. All the four patterns, herring-bone, brickwork, staircase, and ladder, found in the crystal structures, were displayed and discussed. An attempt to correlate the molecular shape with the aggregation type is given.