To optimise combustion in a wide field of applications, lasers represent attractive future alternative ignition sources, especially for internal combustion engines. Experiments were carried out in a high pressure, constant volume chamber (up to peak pressure and initial temperature of ). Laser induced ignition of different hydrogen–air mixtures (air/fuel equivalence ratio λ=1.8–8) was investigated, using different filling pressures (p=0.5–), different ignition energies (pulse energy PE=1–), different chamber temperatures (T=393–) and different focal length lenses (f=60, ). A Q-switched Nd:YAG laser at with a pulse duration of about was used for ignition. An InGaAs photodetector (800–) and a piezoelectric pressure transducer were used to characterise the combustion. Gas mixtures between λ=2.5 and 3.6 showed knocking combustions. With increasing initial pressures the minimum pulse energy was decreasing.