Fractional dispersed phase hold-up and dispersed side mass transfer coefficients for bovine serum albumin (BSA) and amyloglucosidase (AMG) were measured in 50 mm i.d. York-Schiebel columns using salt-polyethylene glycol (4000), potassium phosphate-PEG and sodium sulphate-PEG systems. The effect of column height and the effect of phase compositions of the aqueous phase system were studied. The critical impeller speed for flooding and the critical superficial dispersed phase velocity for flooding were measured. Empirical correlations have been developed for fractional dispersed phase hold-up and dispersed side mass transfer coefficients. The performance of the York-Scheibel column has been compared with that of the spray column.