A novel analysis to determine the spreading pressure, pi(w), for water-polymer interactions from contact angle data is proposed by using Van Oss et al.’s interfacial Lifshitz-van der Waals and acid/base interactions method. In this analysis, first measurements of the contact angles of water drops on the polymer in different hydrocarbons in the two-liquid method are performed; then the contact angle determination of a water drop on the same polymer sample in the one-liquid method is carried out. The data obtained from the one-liquid method are evaluated by using the data obtained from the two-liquid method in order to calculate pi(w). The precise contact angle data on poly(tetrafluoroethylene)(PTFE), poly(methylmethacrylate) (PMMA), and poly(vinyl chloride) (PVC) reported by Tamai et al. are used in the calculations and good agreement is obtained with the pi(w) data obtained from independent adsorption measurements.