Water transport in a densely crosslinked epoxy network, TGDDM-HHPA, was investigated by coupling time-resolved FTIR spectroscopy and gravimetric measurements. Vibrational analysis yielded information on the different water species present in the system and allowed a quantitative estimation of their population at sorption equilibrium. The transport of water molecules was found to follow a Fickian behaviour characterized by an effective diffusion coefficient which increases with total water concentration. The dependence of the effective diffusion coefficient, D-eff(C), on concentration, as obtained from integral sorption curves, was interpreted by introducing a concentration dependent term, D(C), and an "interaction factor", phi, which accounts for the effect of the molecular interactions which effectively slow down the diffusion process. The results were compared with those obtained on another epoxy network, TGDDM-DDS, characterized by the presence of stronger interacting sites. Differences and similarities of the spectroscopic and gravimetric results are critically discussed in the light of the structure of the two networks. (c) 2006 Elsevier Ltd. All rights reserved.