Differential electron emission occurring as the result of fast hydrogen atom impact on helium and argon targets has been studied using standard noncoincidence and emitted-electron-iom'zed-projectile coincidence techniques. Impact energies were 0.5 and 1 MeV; electron emission was measured between approximately 20 and 2000 eV for selected laboratory emission angles ranging from 0° to 180°. The data demonstrates the importance of simultaneous target-projectile ionisation as previously observed for energetic He + impact. The experimental data for the helium target, when compared to PWBA calculations using hydrogenic wave functions, indicate good agreement with theory for projectile ionisation and, indirectly, reasonably good agreement for target ionisation. Simultaneous target-projectile ionisation events were not included in the model. The argon data are compared with more sophisticated calculations for electron loss. These comparisons indicate the importance of second order effects at large emission angles.