We examined the physical and chemical characteristics of colloidal dispersions of fullerene materials (nC(60)) produced through several solvent exchange processes and through extended mixing in water only. The nC(60) produced via the different methods were unique from each other with respect to size, morphology. charge, and hydrophobicity. The greatest dissimilarities were observed between the nC(60) produced by extended mixing in water alone and the nC(60) produced by solvent exchange processes. The role of the respective solvents in determining the characteristics of the various nC(60) were attributed to differences in the solvent-C-60 interactions and the presence of the solvent as a residual in the nC(60) structure, indicating the significance of the solvent properties in determining the ultimate characteristics of the colloidal fullerene. Thus, fullerene C-60 that may become mobilized through natural processes (agitation in water) may behave in dramatically different ways than those produced through more artificial means. These results highlight the difficulties in generalizing nC(60) properties, particularly as they vary in potential toxicity considerations.