The alloy In_1-xGa_xSb has been identified as potentially an important component in mid-infrared laser diodes which use band structure engineering of quantum structures based on the narrow-gap III-V material InSb. A pump-probe measurement has been made of carrier recombination in bulk In_1-xGa_xSb, for a range of alloy compositions. Over the range of excited carrier densities (5 × 10¹⁶-3 × 10¹⁷ cm^-3) and at the temperatures (30-300 K) studied experimentally, contributions to the recombination from Auger, Shockley-Read-Hall and radiative mechanisms were calculated using an analytic approximation, with carrier degeneracy included. Excellent agreement with experiment was obtained over the alloy range x = 0.0-0.2 (corresponding to a room-temperature energy gap variation from 0.175 eV to 0.215 eV). Numerically the room-temperature Auger coefficient, C, decreased from the value 1.17 × 10²⁶ cm⁶ s^-1 at x = 0 (i.e. InSb) to 0.98 × 10²⁶ cm⁶ s^-1 at x = 0.2. The fact that C decreases with energy gap increase, in good agreement with theoretical predictions, is important for strained layer quantum well device applications.