By the reaction of m-cresol as a microbicide with acryloyl chloride m-cresyl acrylate (CA) was synthesized, and polymers with the moiety of m-cresol were prepared by the radical terpolymerization of CA -methylmethacrylate -acrylic acid. The contents of CA unit in the polymers were found to be 4.7 mol% and 10.1 mol% from their nuclear magnetic resonance spectra. The number -average molecular weights of the polymers were in the range of 12000 to 15000. Through the hydrolysis of the polymers m-cresol was released. The release rate of the microbicide increased with increasing PH of the release medium. This result can be attributed to enhanced proton dissociation of carboxyl group of the acrylic acid unit in the polymers. These polymers showed microbicidal activities for S. aureus as a positive microbe and E. coli as a negative microbe.