The optical band gap energy and the dielectric functions of n-type 4H–SiC have been investigated experimentally by transmission spectroscopy and spectroscopic ellipsometry and theoretically by an ab initio full-potential linear muffin-tin-orbital method. We present the real and imaginary parts of the dielectric functions, resolved into the transverse and longitudinal photon moment a, and we show that the anisotropy is small in 4H–SiC. The measurements and the calculations fall closely together in a wide range of energies.