The vapor pressures of 52 compounds including n-alkanes and their monosubstituted derivatives, as well as chloroand alkylbenzenes were determined exploring the gas chromatographic relative retention time (GLC-RT) technique in its simplest form, that is, using a single reference standard and neglecting the activity coefficient effect (GLC-RT1S). The selection of compounds was limited to those which are in the liquid state under the measurement conditions and for which high-quality vapor pressures obtained by direct methods are available at temperatures of GLC measurements. This approach should eliminate possible secondary error sources (such as data extrapolation or recalculation from supercooled liquid to solid phase or vice versa). On the basis of a thorough comparison of the GLC-RT1S-based and directly measured vapor pressures for the group of (functionalired) n-alkanes and by exploiting n-alkanes as reference solutes it is clear that deviations from direct data are significant (in many tens of percent) when single reference compounds are used. However, when an n-alkane that has a retention time lower than the test compound but close to it is used as the reference, the relative errors do not exceed 20%. Overall, the method has been found to be rather reliable over a wide range of conditions for nonpolar and slightly polar substances. For polar compounds, such as alcohols or nitriles, the results do confirm the need to carefully select standards with the same functionality as the targets to be evaluated. In contrast to homologous series no regular pattern can be observed for functionalized benzenes even if the reference compounds were selected from the same group of substituted benzenes.