A multiwavelength differential absorption lidar system for measuring vertical concentration profiles of atmospheric SO₂, NO₂, and O₃ was developed. The system contains two Nd: YAG pumped dye lasers, each capable of alternate oscillation with two wavelengths, and can emit a sequence of four wavelengths in the ultraviolet and visible regions. The geometrical form factor was calculated for biaxial and coaxial configurations, and the former was adopted for its ability to eliminate scattering from close range during long range measurement. The system can be used for high-resolution, multiwavelength DIAL measurement of a single species or simultaneous two-wavelength DIAL measurement of two species. As a preliminary measurement, O₃ concentration was measured in the lower troposphere. The return signals are in agreement with the calculated geometrical form factors, and simultaneous null and DIAL profile measurements show that the instrumental error due to beam misalignment was low.