Terahertz lasers using inter-subband transitions in quantum wells: predictions from Monte Carlo simulation. P. Kinsler, R. W. Kelsall, P. Harrison. Institute of Microwaves and Photonics, School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom. accepted by Physica B We present the first Monte Carlo device simulations of an inter-subband laser, predicting the possibility of lasing in the far infrared (THz) using emission from optically pumped GaAs/AlGaAs triple quantum wells from 77K to 300K. The simulations included a full set of electron--phonon and electron--electron scattering processes, as well as a realistic model for optical pumping. The THz band has important potential applications in imaging (e.g. medical, high resolution radar) and short-range communications (e.g. wireless office networks). Email: Dr.Paul.Kinsler@physics.org