The transport characterization of aromatic polyamide hydrazide (APAH) ultrafiltration membranes has been discussed. The average pore radius of these membranes are evaluated using modified poiseulle＇s flow and gaseous permeation methods. Separation of polyethylene glycols (PEG) of varying molecular weights and complexed polyvalent ionic species across these membranes are reported as a function of applied pressure. The molecular weight cut off (MWCO) of these membranes are predicted using Sourirajan＇s preferential sorption and capillary flow mechanism and are compared with experimental values in order to test the applicability of the mechanism for such membranes. The chemical and radiation stability aspects of these membranes are also discussed.