Constant-rate and constant-pressure microfiltration experiments were carried out using dilute colloids of binary mixtures of polystyrene latex particles with two different sizes and the microfiltration membranes, making them essentially impermeable to larger particles but permeable to smaller particles, and both filtration behaviors were examined. In addition to the measurement of the rejection of smaller particles with the progress of filtration, the pressure rising and flux decline behaviors were measured in constant-rate and constant-pressure filtration experiments, respectively. As suggested by the plots based on the characteristic filtration form for the blocking filtration laws, in each case of constant-rate and constant-pressure filtration, the filter cake comprised of larger particles initially formed, and subsequently smaller particles were trapped in the pores of the filter cake of larger particles. Eventually, a binary cake of both larger and smaller particles grew up, indicating a much higher specific cake resistance than that of larger particles alone. The capture of smaller particles was accelerated by the decrease in the filtration rate in constant-rate filtration and the decrease in the filtration pressure in constant-pressure filtration, and this contributed to the remarkable increase in the filtration resistance. The logistic growth equation was used to describe the variation of the rejection of smaller particles during the course of filtration. A generalized filtration equation applicable to both constant-rate and constant-pressure filtration processes was proposed with the use of the logistic growth equation in consideration of the total cake resistance represented by adding the increased cake resistance caused by the capture of smaller particles to the sum of the cake resistance of larger particles alone and the membrane resistance. The validity of the model presented here was confirmed by the fact that the calculations based on the model were in relatively good agreement with the experimental data of filtration behaviors obtained under various experimental conditions.