Optical absorption measurements at the fundamental absorption edge in high purity and stochiometrically doped p-type Hg0.7Cd0.3Te show the absorption edge to be significantly influenced by valence band tailing due to native Hg vacancy acceptor defects. The absorption coefficient αe for transitions across the band gap increases as αe=α0 exp k(E−E0); for high purity Hg0.7Cd0.3Te at ambient temperatures k=148 eV−1, this value decreases to k=105 eV−1 at acceptor concentrations of around 2×1016 cm−3.