In this paper, two methods for measuring the equilibrium vapor sorption in polymers are critically compared and data on sorption of toluene, p-xylene, hexane, cyclohexane, and heptane in low density polyethylene are reported. The vapor phase calibration method (VPC) was used to measure vapor sorption at low vapor activities in air (below 0.01), and the gravimetric method was used to measure sorption over wide range of activities of pure vapors (0.1-0.9). The Flory-Huggins interaction parameter (in amorphous phase) varied between 1.00 for cyclohexane and 1.19 for toluene. The resulting confidence intervals are conjunctive, indicating that both methods provide consistent results.