Exposure to harmful radiation is one of the major threats to human beings in outer-space; however, the biological consequences of long term exposure are not well understood. It would be useful to have a means of measuring the effect of space radiation on a living organism during space flights. We conducted a pilot project as part of the International Caenorhabditis elegans Experiment First Flight (ICE-First) project on the International Space Station (ISS). Using a mutational capture system, the eT1 balancer, along with other mutation detection systems, we analyzed the mutational effects of the 11 day mission. Upon recovery, classical genetic approaches and comparative genomic hybridization (CGH) microarrays were used to isolate and characterize mutant strains. Although in this short period of time, as expected no increase in mutational background was observed, we were able to demonstrate the potential of this system for longer-term measurement of biological damage. A sixmonth exposure experiment using the same system is currently in progress on the ISS. The relative simplicity and robustness of this model system demonstrate its potential for use as a biological dosimeter.