Nitric oxide is formed in the atmosphere through the ionization and dissociation of molecular nitrogen by galactic cosmic rays. One NO molecule is formed for each ion pair produced by cosmic ray ionization. The height-integrated input (day and night) to the lower stratosphere is of the order of 6 × 107 NO molecules cm-2/sec in the auroral zone (geomagnetic latitude Φ ≥ 60°) during the minimum of the sunspot cycle and 4 × 107 NO molecules cm-2/sec in the subauroral belt and auroral region (Φ≥ 45°) at the maximum of solar activity. The tropical production is less than 10-7 NO molecules cm-2/sec above 17 km and at the equator the production is only 3 × 106NO molecules cm-2/sec.