The mechanism of addition of various "living" anionic polymers on C-60 has been investigated in apolar and polar solvents, and well-defined star-shaped macromolecules with a C-60 core have been prepared. In toluene, only addition of the carbanions onto double bonds on the fullerene is observed. The maximum number of grafted chains depends on the reactivity of the carbanion borne by the chain; this value is six for the very reactive "living" polystyrene and polyisoprene but only three using the more stable diphenylalkyl carbanion. The number of grafts can be, to some extent (3-6), controlled by stoichiometry. In THF, the reaction mechanism is more complicated : 2 electrons ape first transferred from the carbanions to the fullerene producing the C-60 dianion and then addition takes place. The number of grafted chains depends not only on the reactivity of the carbanion but also on its "bulkiness" : four chains are grafted with tile carbanion styryl, three with 2-vinylpyridyl, and none using diphenylethyl.