Assessment of C 60 nanotoxicity requires a variety of strategies for dispersing it into biological systems. Our objective was to determine organic solvent/surfactant combinations suitable for this purpose. We used Escherichia coli (ATCC# 25254) to determine the cytotoxicity of C 60 in solvents at concentrations up to 100ppm. In this preliminary study we hypothesized that C 60 toxicity is directly correlated with its degree of dispersion in solution and that more solubilizing solvents induce higher toxicity. Test solvent concentration (1%) and Tween 80 (0.04%) were based on E. coli viability assay. Sonication was used to further enhance C 60 dispersal. The end-point response was measured with viability (in terms of LC 50 ) and general metabolic activity (in terms of IC 50 ) of E. coli cultures after exposure. The ultimate goal was to select safe dispersing media and enrich the database of C 60 nanotoxicity for NanoQuantitative-Structure–Activity-Relationship (NanoQSAR) applications. LC 50 range was 30ppm to >400ppm. IC 50 followed the trend. Among the six solvent combinations, DMSO combined with Tween 80 was the optimum combination for defining a dose–response relationship for assessing its toxicity to E. coli. However, N,N-dimethylformamide has the greatest potential to be a safe solvent for C 60 applications based upon its biocompatibility. Solvent solubility alone could not account for the cytotoxicity observed in this study.