Abstract.The first use of an external cavity diode-laser light source in combination with a photoacoustic detector for high-sensitivity gas detection is described. This combined system is applicable for detecting gases with absorption coefficients as low as 510-8cm-1 by operating the photoacoustic cell in an intracavity mode. Measurements were made on the 1.13m absorption lines of water vapour. For quantitative measurements, it was found to be necessary to introduce a reference cell into the system.