Functionalization of C-60 with hydrophilic groups promotes the water solubility of the fullerene core which leads in aqueous solution to the irreversible formation of clusters. Capping the surface of water-soluble fullerene derivatives with surfactants (cetyltrimethylammonium chloride or Triton X-100) was found to exclude formation of fullerene dusters and, in turn, to stabilize fullerene monomers. Flash photolytic and pulse radiolytic techniques were employed to generated excited and reduced states of fullerene monomers and fullerene clusters 1-3. Fullerene aggregation was found to have no significant effects on the physicochemical properties related to the generation and lifetime of the excited singlet state. Nanosecond studies of the processes following photoexcitation revealed noticeable differences between monomeric and colloidal derivatives 1-3 for the absorption maximum of the corresponding *T-1 --> *T, absorptions. Clustering was found to invoke also remarkable changes for the decay of the fullerene’s excited triplet state. Similarly, lambda(max) of the pi-radical anions 1-3 is very sensitive to the environmental parameters of the accommodating assembly. In surfactant media, the maxima ([(C-60(.-))(C4H10N+)](surfactant) 1010 nm) were generally blue-shifted relative to the analogous gamma-CD complexes ([(C-60(.-))(C4H10N+)]/gamma-CD 1030 nm). On the basis of comparison with. fullerene clusters and gamma-CD-incorporated complexes, evidence was found that suggests the presence of fullerene monomers in a core(fullerene)-shell(surfactant) type structure.