This article summarizes summative evaluation of the impact on public radio listeners of Earth & Sky, a short-format science radio program airing daily on more than 1,000 commerical and public radio stations in the U.S. as well as on satellite and Internet radio outlets. Earth & Sky’s goals are to make science accessible and interesting and to increase science literacy by providing daily doses of science to listeners with a range of science backgrounds, knowledge and interest. Subsequent to listening to Earth & Sky, the producers hope listeners may be motivated to turn to other sources of