We describe the performance of 3 m long fiber optic light guides that we have fabricated as part of a search for the rare decay + e+ + at LAMPF. The acceptance cone of the light guides is narrow, leading to substantial ( 80%) light loss entering th guides. But those photons that do fall within the acceptance cone are transmitted long distances without significant further loss. We discuss our fabrication techniques and the results of both bench tests and in-beam tests of complete assemblies. 1988.