We measured the dry flux of nitric acid vapor to a pasture near Champaign, Illinois during June of 1982. The mass flux was determined by a modified Bowen‐ratio method, employing the surface sensible heat flux and temperature and concentration variations with altitude. We found the daytime average deposition velocity to be 2.5±0.9 cm/s. The average canopy (stomatal and adsorption) resistance averaged virtually zero. The measured June dry flux of HNO3was of the same magnitude as the wet flux measured near