Optical-reflectivity data are presented for Rh and Ir for a photon energy range between 0.2 and 40 eV. Strong interband structures are observed in the calculated dielectric functions and optical conductivities, and these are discussed in terms of recent energy-band calculations. The dielectric functions are used to calculate the electron-energy-loss functions. Both metals are shown to possess the characteristic double pair of surface and volume plasmons, though the higher-energy pair is strongly distorted by interband absorption occurring near ℏωp.