A number of lines of the &ngr;3 band of hydrogen cyanide have been detected in solar absorption spectra recorded near sunrise and sunset at Kitt Peak National Observatory (elevation 2095 m) with a 0.01-cm-1 resolution Fourier transform spectrometer. Analysis of two of the strongest and best isolated lines has led to a value of 2.73¿1015 molecules cm-2 for the vertical column abundance of HCN above Kitt Peak. The accuracy of this value is estimated as ¿25%. This result, combined with the stratospheric concentration of HCN derived by Coffey, Mankin, and Cicerone (1981), yields 166 parts per trillion by volume for the average mixing ratio of HCN between 2 and 12 km. This is the first determination of the HCN concentration in the nonurban troposphere.