A major problem facing the development of phase-inversion membranes is macrovoid formation, which adversely affects mechanical properties of the final product. Our molecular modeling studies indicate that these macrovoids can be eliminated upon the addition to the aqueous coagulant of : (i) high amounts of polymer solvent, at the expense of a decrease in coagulation rate or (ii) high concentrations of a salt that is poorly miscible in the polymer solvent, with no associated decrease in coagulation rate.