A static reaction chamber attached to a mass spectrometer was employed to study the adsorption of NO and NO2 onto cold surfaces of pure ice and liquid/solid 70 wt % H2SO4. No significant adsorption could be observed for surface temperatures in the range 193--243 K and NO/NO2 partial pressures of 10-2--10-5 mbar. This sets an upper limit on the uptake coefficients for both NO and NO2 of 5¿10-5. The possible formation of nitrosyl sulphuric acid by adsorption of NO and NO2 on cold sulphuric acid particles is therefore unlikely to be of importance in the stratosphere. ¿ American Geophysical Union 1993