This technique for measurement of cake thickness makes use of a He-Ne laser beam and an optical captor; it relies on the absorption of light by the cake. Measurement of the thickness is made at a single point on the membrane and it is assumed that the cake build-up is uniform along the whole area of the membrane. This technique estimates the growth of cake under real crossflow microfiltration conditions without disturbing the deposition phenomena. The objective of the present study is to validate the dynamic measurement of cake formation and to understand the fundamental mechanisms of fouling in crossflow filtration processes.