Protein fractionation using ultrafiltration is feasible after extensive process optimization. However, conventional process optimisation methods are time consuming and require large amounts of pure proteins, which are sometimes very expensive. Pulsed sample injection ultrafiltration allows rapid determination of sieving coefficient data and may prove to be an efficient process optimisation technique. Very small amounts of pure protein are required for these experiments. A 'quasi-steady state' approximation is proposed fur calculating the actual bulk and membrane surface concentrations from permeate concentration data. The sieving coefficient data obtained from the pulsed sample injection technique are in good agreement with data obtained from 'steady-state' ultrafiltration experiments. Experimental data clearly suggest that for a given permeate flux, the sieving coefficients art: independent of the value of the feed concentration. The permeate concentration-time curves show that at higher permeate flux, lower time duration is required for the development of concentration polarization.