Continuous-wave laser oscillation with a long optical-fiber resonator has been observed. The fiber resonators that were examined were 1. 65, 11. 3, and 101 m long, and longitudinal self-beat spectra of laser oscillations were confirmed with a 1. 15- mu m He-Ne laser; the observed frequencies were in good agreement with the calculated ones. By using a spectrum analyzer, the spectral amplitude was found to be modulated, which is attributable to the fact that a complex Fabry-Perot resonator was formed by reflections on a lens and an input portion of the optical fiber. 14 refs.