An efficient and reliable gas chromatography (GC) method has been developed for measuring mutual solubilities of alkylbenzenes and water. The reliability and precision of the method are demonstrated for toluene and water in the temperature range 303-373 K at pressures within 1 bar of the three-phase curve. The reproducibility of the GC analysis of a given sample is excellent; the absolute average percentage deviation of the analysis is consistently less than 1.0%. The method has also been used to determine the solubility of other alkylbenzenes in water at concentrations as low as 10 ppm (mass), and water solubility in alkylbenzenes as low as 300 ppm (mass). The average percentage deviation of these measurements is less than 6.0%, due largely to the high precision of the GC analysis. The method developed here minimizes the use of sophisticated analytical instrumentation, which makes it suitable for routine analysis. The method employs a GC equipped with a standard thermal conductivity detector, and a single column is used for analysis of samples of both the organic and the water phases. The overall time required for a single analysis is less than 15 min.