The influence of the carrier gas on vapor pressure (psat) measurements by the gas saturation method was studied. Eicosane (C20H42) was used as the test compound. Helium (He), nitrogen (N-2), carbon dioxide (CO2), and sulfur hexafluoride (SF6) were chosen as the carrier gases. The apparent psat of eicosane was determined repeatedly in each of the four carrier gases at 323.15 K, and was found to increase with carrier gas in the order He < N-2 < CO2 < SF6. On average, the apparent psat was 26% higher when measured with SF6 than when measured with helium, which shows that the assumption of ideal-gas behavior for gas saturation measurements can lead to large errors.