Due to their unique properties, fullerenes, a model of carbon-based nanoparticles, have attracted considerable interest in many fields of research including material science and biomedical applications. The potential and the growing use of fullerenes and their mass production have raised several questions about their safety and environmental impact. Available data clearly shows that pristine C60 has no acute or sub-acute toxicity in a large variety of living organisms, from bacteria and fungal to human leukocytes, and also in drosophila, mice, rats and guinea pigs. In contrast to chemically--either covalently or noncovalently--modified fullerenes, some C60 derivatives can be highly toxic. Furthermore, under light exposure, C60 is an efficient singlet oxygen sensitizer. Therefore, if pristine C60 is absolutely nontoxic under dark conditions, this is not the case under UV-Visible irradiation and in the presence of O2 where ffullerene solutions can be highly toxic through 1O2 formation. This chapter offers a general review of the studies on the toxicity of [60]fullerene or C60, the most abundant fullerene, and its derivatives.