The measurement of the complex dielectric constant (e* = e' -j e") in the dipolar absorption domain of the "free" water molecule (microwave region) permits us to follow quasi-speciflcally and precisely the water circulation during the coalescence proces s of a latex. Weight losses and dielectric constants variations have been simultaneously recorded upon latex drying, in a resonant cavity at 5 and 9 GHz and under controlled atmosphere and temperature. Two different latexes were studied (polybutylacrylate (PBuA) and polystyrene (PS)) from which the glass transition temperature effect was investigated. It is found that the harder the polymer particles, the more clearly evidenced the flocculation and packing points are. This method appears to be quite reliable for discriminating the various steps in the film formation process of latexes.