The effects of different substituents on thiacarbocyanine and indocarbocyanine dyes on their adsorption to AgBr microcrystals and on size distributions of J-aggregates were investigated by analytical color fluorescence electron microscopy (ACFEM). The results showed that the adsorbability of the indocarbocyanine iodide dye on cubic AgBr grains was greater than that on the T-grain AgBr. On the other hand, adsorbability of the thiacarbocyanine triethyl ammonium salt on the T-grain AgBr was greater than on the cubic AgBr. In addition, adsorbabilities of 5-substituted thiacarbocyanine dyes either on T-grain or on cubic AgBr were much greater than those of 5- unsubstituted thiacarbocyanine dyes. We inferred that growth of J-aggregates on AgBr could be egarded as Ostwald ripening, and that substitution of the indocarbocyanine with an N-ethyl substituent led to strong J-aggregation. The average size of J-aggregates of 5-substituted thiacarbocyanine dyes formed on cubic AgBr were larger than the average size of J-aggregates of the 5-unsubstituted.