A new graphical procedure is proposed to estimate the interface resistivity in terms of interface mass transfer coefficient (k) in gas-oil pressure decay experiments. We provide a time-domain closed-form analytical solution by the use of Integral Method (IM) to the equations governing the gas-phase-pressure decay with the improved time-dependent gas-oil interface boundary condition. A graphical technique, derived from this analytical solution, is proposed to extract the interface mass-transfer coefficient and Henry's constant. Application of this method to synthetic and experimental pressure-decay data shows that the estimated parameters are in agreement with those reported in the literature. The proposed procedure, coupled with a graphical technique to estimate the diffusion coefficient, is an asset for a simple, quick, and reliable estimation of interface mass-transfer coefficient and Henry's constant. (C) 2016 Elsevier Ltd. All rights reserved.