The KMnO4 oxidation reaction of C60 or C70 fullerenes in benzene solution proceeds smoothly and almost quantitatively in presence of the crown ether 18-crown-6 as phase-transfer agent. The oxidation reaction was followed spectrophotometrically from the early stages to the completion. Essentially fullerenols or polyhydroxylated fullerenes were produced as confirmed also by FT-IR spectroscopy. The resulting degree of hydroxylation of both C60 and C70 was determined as C60(OH)28 and C70(OH)26. As secondary structures, also epoxide and carboxylic groups were detected.