A number of 2-, 4-and 7-substituted benzothiazole derivatives were synthesized to inquire into the relationship between the fluorescence of metal chelates and their structures, and to investigate their applications as analytical reagents. The color and fluorescence reactions of metal ions with these benzothiazole derivatives were investigated by spot tests. On the formation of metal complexes in solution, the color change of 2-substituted derivatives was more remarkable than that of 4-and 7-substituted. As fluorometric reagents for metal ions, however, 4-aminobenzothiazole derivatives were superior to 2-amino and 7-aminobenzothiazole derivatives. 7-Substituted derivatives were inferior in the reactivity with metal ions to 2-and 4-substituted.