The optical properties of W are presented between 0.15 and 33 eV. The optical absorptivity or reflectivity was measured at near-normal incidence, and the data were Kramers-Kronig analyzed to determine the dielectric functions. Drude parameters were determined at low energy and were used to separate interband and intraband contributions to ε2. Structures in ε2 were apparent at 0.42, 0.97, 1.82, 2.35, 3.42, 5.25, 8.8, 11.3, 16.5, 22.5, and 31.5 eV. These features were discussed in terms of recent calculations of Christensen and Feuerbacher and by analogy to other transtion metals studied. The loss functions were shown to have three volume plasmons (25.3, 15.2, and 10.0 eV) and three surface plasmons (20.8, 14.8, and 9.7 eV). Structure near 31.5 eV was interpreted as due to NVII core transitions.