Rotation of the gamma subunit in chloroplast F(1)-ATPase (CF(1)) was investigated by using a single molecule observation technique, which is developed by Noji et al. to observe the rotation of a central gamma subunit portion in the alpha(3)beta(3)gamma sub-complex of F(1)-ATPase from thermophilic Bacillus PS3 (TF(1)) during ATP hydrolysis [Noji, H. et al. (1997) Nature 386, 299-302]. We used two cysteines of the gamma subunit (Cys-199 and Cys-205) of CF(1)-ATPase, which are involved in the regulation of this enzyme, to fix the fluorochrome-labeled actin filament. Then we successfully observed a unidirectional, counter-clockwise rotation of the actin filament with the fluorescent microscope indicating the rotation of the gamma subunit in CF(1)-ATPase. We conclude that the rotation of the gamma subunit in the F(1)-motor is a ubiquitous phenomenon in all F(1)-ATPases in prokaryotes as well as in eukaryotes.