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Abstract: This paper investigates the microfiltration of skim milk in order to separate caseins micelles from two whey proteins, α-lactalbumin (α-La) and β-lactoglobulin (β-Lg), using a modified dynamic filtration pilot (MSD) consisting in 6 ceramic 9-cm diameter membrane disks of 0.2μm pores, rotating around a shaft inside cylindrical housing. A comparison was made with another dynamic filtration module consisting in a disk rotating near a fixed PVDF 15.5cm diameter membrane with 0.15μm pores. Maximum permeate fluxes were 120Lh−1 m−2 with the MSD module at 1930rpm and at 40°C, and 210Lh−1 m−2 at 2500rpm and 45°C, with the rotating disk module. Casein rejection was around 99% at high speed for both membranes. α-La transmission decreased with increasing transmembrane pressure (TMP) from 75% to 60% for ceramic membranes and from 25% to 10% for the PVDF one. β-Lg transmissions were lower, ranging from 23% to 15% for ceramic membranes and from 20% to 5% for the PVDF one. In a concentration test with the PVDF membrane at 2000rpm, the flux decayed from 200Lh−1 m−2 at initial concentration to 80Lh−1 m−2 at VRR=3.2 and 22.1% of the initial α-La mass was recovered in the permeate, against 8.1% for β-Lg. Permeate fluxes in the mass transfer limited regime (J lim) of the MSD and rotating disk module operated at various speeds were well correlated by the equation J lim =17.13 V av where V av denoted the disk azimuthal velocity averaged over the membrane area. Measurements of J lim, taken from Ref. [G. Samuelsson, P. Dejlmek, G. Tragardh, M. Paulsson, Minimizing whey protein retention in crossflow microfiltration of skim milk. Int. Dairy J. 7 (1997) 237–242] during MF of skim milk using tubular ceramic membranes at velocities from 1.5 to 8ms−1 with permeate co-current recirculation were found to obey the same correlation. [Copyright &y& Elsevier]