A strong solvatochromic effect leading to the loss of the fine structure of UV-visible spectra and to the change of the specific absorption was observed for C-60 and C-70 fullerenes in N-methylpyrrolidinone (NMP). The C-60 and C-70 fullerene interactions in NMP solutions were studied by using time resolved fluorescence polarization anisotropy and dynamic light scattering techniques aiming to the determination of fullerene sizes. The process was studied as time dependent in toluene/NMP solutions and both the formation of fullerenes aggregates and specific interactions between fullerenes and NMP were observed. (c) 2005 Elsevier B.V. All rights reserved.