The purpose of this study was to determine whether or not 5 nm AgNPs can be tested successfully for genotoxicity hazard using the Ames test and the in vitro micronucleus test in TK6 human lymphoblastoid cells. Although bacterial mutagenicity assays are common to all genotoxicity batteries, the antibacterial properties of AgNPs may limit the concentrations of the test article that can be assayed. It is possible that the test may be inappropriate for evaluating AgNPs. Also, although AgNPs have tested positive for micronucleus induction in other systems, TK6 cells have recently been proposed as more appropriate than the rodent cell lines that are more commonly used for genotoxicity testing [34] and [35]. It is of interest, therefore, to evaluate the ability of AgNPs to induce micronuclei in TK6 cells.