Volcanic gas from an inaccessible fumarole at Aso volcano, Japan, was recently measured with a Fourier Transform InfraRed (FT-IR) spectral radiometer. Absorption features of CO, COS, CO2, SO2, and HCl were identified in the volcanic plume spectra. This is the first time the five volcanic gas components are detected simultaneously by a remote technique. Based on the measured CO/CO2 ratio of 2.6¿10-3, the equilibrium temperature of the volcanic gas is estimated to be 750¿¿120 ¿C.¿ 1997 American Geophysical Union