The routine, rapid, and accurate measurement of water in smoke is a challenge, due to the many sources of potential interference. A recent change in gas chromatography instrumentation in the Celanese Acetate Filter Products laboratories provided an opportunity for a detailed examination of some of the factors that affect the measurement of both water delivered in smoke and water retained by the cigarette filter. Since an accurate analysis of water is critical to the calculations of dry tar yield of the cigarette and tar removal efficiency of the cigarette filter, there was special interest in determining sources of water measurement variability. A coulometric Karl Fisher instrument was purchased for the purpose of providing quality assurance for the new test procedure and to assist in obtaining a better understanding of the relative contributions of the solvent, smoke traps, cigarette filters, and other test components, to the total water observed by GC. The ingress of water (from the room air) into the solvent in bulk storage containers, dispensing bottles, and prepared standards was observed over time, and resulted in a revised standard operating procedure for the handling of solvent and standards in our laboratories. The combination of enhanced understanding of water behavior and improved instrumentation has provided a more rapid and robust analysis.