There is a pressing need to develop rapid whole animal-based testing assays to assess the potential toxicity of engineered nano-materials. To meet this challenge, the embryonic zebrafish model was employed to determine the toxicity of fullerenes. Embryonic zebrafish were exposed to graded concentrations of fullerenes [C 60, C 70, and C 60(OH) 24] during early embryogenesis and the resulting morphological and cellular responses were defined. Exposure to 200 μg/L C 60 and C 70 induced a significant increased in malformations, pericardial edema, and mortality; while the response to C 60(OH) 24 exposure was less pronounced at concentrations an order of magnitude higher. Exposure to C 60 induced both necrotic and apoptotic cellular death throughout the embryo. While C 60(OH) 24 induced an increase in embryonic cellular death, it did not induce apoptosis. Our findings concur with results obtained in other models indicating that C 60(OH) 24 is significantly less toxic than C 60. These studies also suggest that the embryonic zebrafish model is well-suited for the rapid assessment of nanomaterial toxicity.