The case for applying correlation techniques to gas chromatography has been re-examined following the introduction of on-line cross-correlators, and it is concluded that there is still little scope for these techniques in a normal chromatograph situation. A series of experiments designed to demonstrate the feasibility of applying cross-correlation to trace analysis by gas chromatography is reported and, from these experiments, it is concluded that correlation offers considerable advantages over the conventional single-sample injection method when minute quantities of a component in a sample gas are being sought. With the continuing interest in environmental pollution, there appears to be much scope for correlation techniques in this area.