We present measurements of tropospheric O3, SO2 and aerosol from a volcanic emission event using new multi-wavelength differential absorption lidar (DIAL) techniques that enable us to remove the mutual effects between O3 and SO2 from the raw measurements. The aerosol extinction coefficient is retrieved directly from the lidar return signal at the “off” wavelength and is used to estimate aerosol effects on O3 and SO2measurements. Null error, statistical error, and absorption cross-section error are also analyzed. The O3 and SO2 concentrations at height between 1000 m and 2000 m for a volcanic event on September 10, 2001 were about 20 ppb and 10–35 ppb, respectively, with an error less than 10 ppb. The measured SO2 concentration was much higher than the normal SO2 background value (∼1 ppb) in the troposphere. We also measured O3 concentrations from 13 December 2000 to 06 January 2001 and investigated O3 diurnal variation during a 24-hour period on November 24, 2000. A high O3 concentration of about 250 ppb was observed in late December 2000.