A highly solvent- and heat-resistant ultrafiltration membrane based on poly(p-phenyleneterephthalamide) (PPTA) was prepared by phase-inversion method, using concentrated sulfuric acid and water as solvent and nonsolvent, respectively. The uniform formation of membranes was obtained in the concentration range of the PPTA solutions up to ca. 8-9 wt.%. An attempt to control membrane performances was made by changing the polymer concentration in the casting solution and the gelation bath temperature. The solvent- and heat-resistance of the membranes was tested by immersing them for a long period in various kinds of solvents and in boiling water. The shrinkage of the membrane due to interaction with solvents was found to be very small and the membrane was also stable in boiling water as well as in various solvents. It was found that the effects of solvents and heat on membrane performances are insignificant.