Electron transport in relaxed InxGa1-xAs materials has been investigated as a function of temperature (4.2 to 300 K) and pressure (0 to 8 x 10(8) Pa) for a wide range of alloy compositions. A dramatic decrease in both the mobility and carrier concentration in a limited alloy composition range x=0.30 to 0.60 has been observed. The results were analyzed using an iterative solution of the Boltzmann equation (ISBE) based on the usual scattering mechanisms. Both the measured temperature and pressure dependence of mobility and carrier concentration together with the ISBE calculations indicate that the deep levels are responsible for the sharp decrease both in mobility and carrier concentration in the alloy composition range x=0.30 to 0.60. For the x=0.51 and 0.60 layers an additional scattering mechanism having a temperature dependence of similar to T-2.6 has been observed, which is attributed to electron scattering from the deep levels generated in association with the layer relaxation.