Room‐temperature photoreflectance measurements were used to determine the radial and axial distribution of low levels of indium in 3‐in.‐diameter semi‐insulating bulk GaAs materials grown by the liquid‐encapsulated Czochralski method. These results were compared with 4.2‐K photoluminescence data and found to be accurate and more convenient for this application. Room‐temperature photoreflectance allows an accurate determination of the indium content in the range of mole fraction 0.1%–2.0% with standard deviation of 0.03%. Two types of radial inhomogeneity were found in commercially available GaAs wafers. This is discussed in terms of indium segregation and shape of solid and liquid interface during the crystal growth.