We report an observation of a clean-surface reconstruction of a simple metal, a (1 × 3) structure on Be(1120). Kinematic analysis of low-energy electron diffraction indicates that the (1 × 3) reconstruction involves the displacement of atomic chains at the surface. The stabilities of the unrelaxed, bulk terminated surface and two proposed models based on missing rows were calculated using a first-principles pseudopotential method within the local-density approximation. Our results indicate that surface relaxation must be the determining factor in the stability of the reconstruction. Since Be has no occupied d-bands, the mechanism driving the reconstruction must be different from that of transition- and noble-metal missing-row reconstructions.