The potential explosion hazard of mixtures containing ammonia and nitric oxide was investigated in a constant-volume preheated test cell. Ammonia/air and ammonia/nitric oxide mixtures were centrally spark-ignited in the cell at initial temperatures from 25 to 220 degrees C and initial pressures from 101 to 450 kPa. The ammonia/air mixtures produced the expected results for flammability limit, agreeing well with values from the literature. The ammonia/nitric oxide mixtures are capable of producing powerful explosions with laminar burning velocity over 1 m s(-1) and a pressure rise over ten times the initial pressure. Also, when mixing nitric oxide, oxygen and ammonia, it was found to be possible to produce mixtures which reacted and self-ignited on mixing. The paper presents flammability limits and burning velocities as functions of temperature, pressure and gas concentration.