The porous copolymer films of N-methacryloyl-L-alanine methyl ester and diethyleneglycolbis-allylcarbonate (diallyl oxydiethylene dicarbonate) were hydrolyzed with 1 M NaOH solution for 40 min at 25 degrees C. The pores of the films showed pH response in diameter. The pore diameter of 3,7 mu m in the buffer solution of pH 3 was closed completely at pH 5.