Musk ketone, a synthetic musk fragrance ingredient that has been found in river water, fish and breast milk, was evaluated for potential genotoxicity in a battery of short-term tests. The mouse lymphoma assay was conducted at musk ketone concentrations ranging from 700 to 4000 micrograms/ml and 2.0 to 35 micrograms/ml in the absence and presence of rat liver S-9, respectively. No increased mutant frequencies were noted. An in vitro cytogenetics assay in Chinese hamster ovary cells was conducted at musk ketone concentrations ranging from 4.3 to 34 micrograms/ml and 1.25 to 10 micrograms/ml in the absence and presence of rat liver S-9, respectively. On the basis of the non-reproducibility of a statistically significant increase at a single concentration and no increases in other test systems, musk ketone was concluded to be negative for chromosome aberrations. An in vitro unscheduled DNA synthesis (UDS) assay was conducted in primary rat hepatocytes at musk ketone concentrations between 0.5 and 5.0 micrograms and 50 micrograms/ml. No increases in net nuclear grain counts were noted. Musk ketone did not show genotoxic potential based on the negative results in the mouse lymphoma, in vitro cytogenetics and in vitro UDS assays.