The reactivity of halogenofullerenes, C60Cl6 and C60Brn (n = 6, 8), was elucidated in four different solvents, CHCl3, benzene, CS2, and cyclohexane, in the absence and in the presence of organic donors of tetrathiafulvalene (TTF) type. In the absence of any electron donors, the stability order in solution was found to be C60Cl6 > C60Br8 > C60Br6 The nature of the stability has been considered on the basis of the results of semiempirical molecular orbital calculations. In the presence of any organic donors of TTF type employed in this work, C60Br8 decomposed to form C-60 in all the solvents. For C60X6 (X = Cl, Br), a pronounced difference in the reactivity was observed. For an addition of relatively strong electron donor, the dehalogenation of C60X6 resulting in the formation of cation radical of the donor was observed, while for the relatively weak donors, such a behavior was not observed, and no charge-transfer (CT) interactions between C60X6 and the electron donors were optically detected. According to the difference in reactivity with electron donors, the electrical stability order was found to be C60Cl6, C60Br6 > C60Br8 This order corresponds to that of the electron-accepting ability (C60Br8 > C60Br6 > C60Cl6) Obtained by cyclic voltammetry measurements. On the basis of the relationship between the electrochemical properties of the halogenofullerenes and the counter donors, the boundary where a certain CT would begin was first predicted for the C-60 family. X-ray powder diffraction, UV-vis, and elemental analyses revealed that the solid complex prepared in this work by the reaction of C60Br8 With TTF in CS2 was not (TTF)(x)C60Brg (x approximate to 8) but instead TTF . Br-x (x = 0.76-0.86).