Intraband absorption in p-type In.53Ga.47 As has been measured at FIR frequencies (40–240 cm−1). It is found that the absorption in p-type InGaAs, which is associated with transitions between the light- and heavy-hole valence bands, is very strong. The absorption coefficient is as high as 103–104 cm−1. It increases with the doping concentration but decreases with the frequency of the incident radiation and temperature.