The averaged complex dielectric function = ͑2 Ќ + ʈ ͒ / 3 of polycrystalline Ti 2 AlN, Ti 2 AlC, Nb 2 AlC, ͑Ti 0.5 ,Nb 0.5 ͒ 2 AlC, and Ti 3 GeC 2 was determined by spectroscopic ellipsometry covering the mid infrared to the ultraviolet spectral range. The dielectric functions Ќ and ʈ correspond to the perpendicular and parallel dielectric tensor components relative to the crystallographic c-axis of these hexagonal compounds. The optical response is represented by a dispersion model with DrudeLorentz and critical point contributions. In the low energy range the electrical resistivity is obtained from the Drude term and ranges from 0.48 ⍀ m for Ti 3 GeC 2 to 1.59 ⍀ m for ͑Ti 0.5 ,Nb 0.5 ͒ 2 AlC. Furthermore, several compositional dependent interband electronic transitions can be identified. For the most important ones, Im͑ ͒ shows maxima at: 0.78, 1.23, 2.04, 2.48, and 3.78 eV for Ti 2 AlN; 0.38, 1.8, 2.6, and 3.64 eV for Ti 2 AlC; 0.3, 0.92, and 2.8 eV in Nb 2 AlC; 0.45, 0.98, and 2.58 eV in ͑Ti 0.5 ,Nb 0.5 ͒ 2 AlC; and 0.8, 1.85, 2.25, and 3.02 eV in Ti 3 GeC 2 .