This paper describes the development of an analyser intended to measure the concentrations of CO2 and O-2 present as part of the gas mixture in the head-space of food packages. The efficiency of the measuring device was evaluated by analysing the atmosphere of packages containing the following food products: grated Parmesan cheese, milk powder and fresh pasta. A comparison between the results of the analysis performed with the newly developed analyser and those obtained by gas chromatography showed good correlation between the two methods. The O-2 and CO2 analyser presented satisfactory accuracy (absolute error smaller than 2.5%, v/v) and precision (relative standard deviation varying from 0.2% to 8.5%). In addition,final results of the levels of both gas types present in the atmosphere submitted to analysis are obtained after about 2 min. The proposed analyser constitutes an alternative solution far the analysis of gases present in the head-space of packages, especially when gas samples of very small volumes - about 200 mu l - are to be used. Copyright (C) 1999 John Wiley & Sons, Ltd.126271275