The application of chitosan as the coagulant/flocculant in a microfiltration process of natural water has been evaluated. In order to study fouling effects, variations in permeation velocity of demineralized water were measured at the beginning and at the end of each microfiltration experiment. Experiments were performed at two different permeation velocities, 45 and 90 L h(-1) m(-2). At the permeation velocity of 45 L h(-1) m (2) microfiltration led to reductions up to 33% of UV254 compounds, 9% of TOC, and 65% of iron, while the coupled coagulation-microfiltration process resulted in a reduction up to 70%, 47% and 100% for UV254 compounds, TOC and iron, respectively. However, increased fouling effects were detected in the coupled process. Similar results were observed when the permeation velocity was fixed at 90 L h(-1) m(-2). Although the coagulation process caused an increase in fouling, the treated water quality was higher comparatively to the simple microfiltration process. This fact was evaluated as an important argument for the application of the coagulation pre-treatment procedure.