Amphiphilic random copolymers, poly(R-HPMA-co-S-PAM) and poly(H-PMA-co-S-PAM), were prepared by radical copolymerization of N-methacryloyl-(S) phenylalanine methyl ester (S-PAM) and N-[(R)-2-hydroxypropyl] methacrylamide (R-HPMA) or N-(2-hydroxypropyl)methacrylamide (HPMA) with various molar ratios of R-HPMA (or HPMA) (m) to S-PAM (n). Either aqueous solution of poly(R-HPMA-co-S-PAM) with the molar ratio of m : n = 0.81 : 0.19 or poly(HPMA-co-S-PAM) with the molar ratio of m : n = 0.79 : 0.21 exhibited the lower critical solution temperature (LCST) at 16 degreesC. The LCST in the presence of (S)-(-)-phenylalanine (S-Phe) shifted from 16 to 20 degreesC and 18 degreesC for poly(R-HPMA- co-S-PAM) and poly(HPMA-co-S-PAM), respectively, whereas the LCST did not shift in the presence of(R-( +)-phenylalanine (R-Phe). Thermosensitive Gel(R-HPMA-co-S-PAM) and Gel(HPMA-co-S-PAM) were also prepared from radical copolymerization of S-PAM and R-HPMA or HPMA in the presence of N,N ' -ethylenebisacrylamide (EBAAm) as a crosslinker. When the gels shrunk at 40 degreesC, the release of dansyl-(R)-phenylalanine (Dans-R-Phe) from the gel in which loaded Dans-R-Phe occurred was more easily done than that of Dans-S-Phe from the gel that loaded Dans-S-Phe. Thus, these thermosensitive copolymers and gels were found to exhibit chiral recognition for phenylalanine derivatives.