The solubilization of [60]fullerene (C-60) in water in the presence of aquatic humic substances (HSs) was investigated by means of a batch method. The apparent water solubility of C-60 in the presence of HSs was 8-540 times higher than that in the blank solution. The size fractionation of C-60 in aqueous solutions of HSs showed that the solubilization was due to the dispersion Of C-60 aggregates as a result of the adsorption of HSs. These results demonstrate that HSs can play a fundamental role in the solubilization of C-60 in natural waters.