In order to improve the performance of membrane processes there is a need to understand the basic phenomena occurring at the membrane and in the bulk fluid. Fluid dynamic gauging (FDG) is a technique that has been used previously to measure the thickness and strength characteristics of a fouling layer on solid surfaces. Here, its application has been extended to investigate the nature of fouling deposition on membranes in dead-end and cross-flow microfiltration. Two modes of FDG measurement are demonstrated, wherein either (i) the mass flow rate of liquid withdrawn through the gauge or (ii) the pressure drop across the nozzle, are fixed. In dead-end filtration, the deposition of ballotini on a polymeric membrane is monitored quantitatively via measurements of thickness and the permeate flux. FDG has also been integrated with imaging techniques to study the deposition and removal processes. In cross-flow, FDG proved to be able to monitor the growth of fouling layers during molasses processing.