The electrochemistry of C-60 in tetrahydrofuran/tetrabutylammonium hexafluorophosphate (THF/TBAH) solutions was thoroughly investigated, and particular attention was devoted to possible interactions occurring between the fullerene and this medium and leading to irreversible modification of C-60 itself. Either untreated or carefully purified solvent was used in the experiments, showing that only in the latter case can reliable results be obtained, the occurrence of irreversible reactions between C-60 and an impurity present in traces (probably peroxides) having been monitored by both cyclic voltammetry (CV) and absorption spectroscopy.