A study has been carried out in three French hospitals in order to assess and model the pharmaceutical load in hospital wastewater and its impact in WWTP. This study, called Mediflux, consisted of three successive steps: first, an original prioritization procedure developed in our laboratory enabled us to select a list of relevant molecules from different Anatomical Therapeutic Chemical (ATC) classes containing pharmaceuticals for specific hospital use such as anesthetics or antineoplastic agents and pharmaceuticals dispensed in the community. Then, analytical quantification procedures were developed and validated according to 2002/657/EC European directive. Sampling campaigns were performed in three different hospitals, two located in the Paris area and one in a medium-sized city 150 km from Paris. Sampling was also carried out in wastewater treatment plants. At the same time, in order to model the pharmaceutical loads from hospitals, predicted concentrations were calculated as a first approach assuming it would be a single-box model, i.e. hospitals have no effect on drug loads and only human metabolism is taken into account to evaluate the fraction of drugs eliminated in hospital effluent. In the last step, the comparison of measured and calculated concentrations showed a satisfactory correlation for some pharmaceuticals, mainly those with short elimination half-lifes and weak human metabolism. For others, it appeared that modeling should take into account various factors such as out patient use, pharmacokinetic data and molecule stability in wastewater.