Within the Life Sciences Division of NASA, the Exobiology Program seeks to understand the origin, evolution and distribution of life in the universe. There are two feasible methods of searching for life beyond the earth. The first is to return to Mars and systematically explore its surface and subsurface with instrumentation capable of identifying extinct as well as extant life. The second is to search for advanced forms of life in other planetary systems that have developed a technology capable of modifying their environment in ways that make it detectable across the vast interstellar distances. The Exobiology Program is currently pursuing both of these options. If NASA s SETI (search for extraterrestrial intelligence) Microwave Observing Project of the 1990s fails to detect evidence of radio signals generated by an extraterrestrial technology, what might be the next step? The establishment of a permanent lunar base early in the next century may enable the construction of large aperture radio telescopes that can extend both the sensitivity and the frequency range of SETI observations. A lunar base may also provide the opportunity for construction of optical and IR telescopes intended for the direct detection of extrasolar planetary systems.