Detecting early ageing stages of seeds in storage is of great concern to vegetable seed companies. Despite their reliability conventional germination tests are destructive and time consuming. One alternative towards assessing the quality of seed is to monitor the concentration of certain volatiles (acting as biological markers) evolved from the seeds; examples are ethanol (EtOH), acetaldehyde, ethane, methanol, etc. Most of the presently used methods have only moderate insensitivity and are therefore not suitable for the on-line measurements. In this work CO laser photoacoustic spectroscopy (LPAS) was used to investigate the on-line evolution of EtOH and acetaldehyde from the imbibed nonaged and aged seeds of cabbage. The overall performance of LPAS was superior to that of Fourier transform infrared and of gas chromatography. (C) 2003 American Institute of Physics.