One of NASA's long-term objectives is to be able to stay on the moon for extended periods, and to provide a stepping-stone for future Mars explorations. The lunar soil simulant JSC-1 has been developed by NASA from volcanic ash found in Arizona to facilitate testing of toxicity and system requirements for lunar exploration. A concentration-response study of JSC-1 was undertaken on the murine macrophage cell line RAW 264.7. Results demonstrated concentrations of 50-2000 microg/ml JSC-1 induced enhanced expression of inducible nitric oxide synthase (iNOS). Data suggest that extraterrestrial regolith has the potential to induce an inflammatory response, and that future development of anti-inflammatory mitigative strategies may be necessary to counteract lunar dust-associated cellular toxicity.