Microbial film development in water conduits causes pronounced increases in fluid frictional resistance and heat transfer resistance which is of major concern to the water supply and power industries. The objective of this study was to better understand the microbial film development process and its effect on fluid frictional resistance. A Tubular Fouling Reactor system was constructed to investigate microbial film development in the laboratory. Glucose was used as the energy source for microbial growth. Fluid frictional resistance in the fouled tube increased to as much as eight times the clean tube condition. Constriction of the tube due to the microbial film does not significantly affect fluid frictional resistance. However, viscoelastic properties and the filamentous nature of the microbial film contribute to the increase in fluid frictional resistance. Growth kinetics and substrate removal were investigated and a model for microbial film production was developed. Experimental data were used to test the validity of the model and good agreement was obtained. The results indicate that fluid frictional resistance and microbial film thickness can be predicted from influent glucose concentration for a given flow velocity.