Graphene and graphene oxide receive much attention these years, because they add attrac- tive properties to a wide range of applications and products. Several studies have shown toxi- cological effects of other carbon-based nanoma- terials such as carbon black nanoparticles and carbon nanotubes in vitro and in vivo. Here, we report in-depth physicochemical characteriza- tion of three commercial graphene materials, one graphene oxide (GO) and two reduced graphene oxides (rGO) and assess cytotoxicity and genotoxicity in the murine lung epithelial cell line FE1. The studied GO and rGO mainly consisted of 2–3 graphene layers with lateral sizes of 1–2 mm. GO had almost equimolar content of C, O, and H while the two rGO materials had lower contents of oxygen with C/O and C/H ratios of 8 and 12.8, respectively. All materials had low levels of endotoxin and low levels of inorganic impurities, which were mainly sulphur, manganese, and silicon. GO generated more ROS than the two rGO materi- als, but none of the graphene materials influ- enced cytotoxicity in terms of cell viability and cell proliferation after 24 hr. Furthermore, no genotoxicity was observed using the alkaline comet assay following 3 or 24 hr of exposure. We demonstrate that chemically pure, few- layered GO and rGO with comparable lateral size (> 1 mm) do not induce significant cytotox- icity or genotoxicity in FE1 cells at relatively high doses (5–200 mg/ml).