The analysis of dissolved gases in power transformer oils is an efficient diagnostic tool for routine performance monitoring of power transformers. A static headspace gas chromatographic method has been developed to automate the analysis. The parametric study showed that initial equilibration time is about 200 min at 70°C and set the sample volume to 15 ml of oil. Distribution coefficient values were determined under these optimized headspace conditions, avoiding the need of subsequent calibration from oil standards. The precision of the method was better than 5% and detection limits for hydrogen, carbon monoxide and methane, carbon dioxide, and hydrocarbons were 7, 10, 5 and 1 ppm (v/v), respectively. The response is linear over 3 decades up to 1000 ppm. A comparison study between the headspace and the currently used ASTM D3612 method using on-line transformer oil samples showed a good agreement. The headspace method permits an increased number of analysis per day, as much as four times, compared to the ASTM method.