Vinyl thiocyanatoacetate (VTCA) was synthesized, and its radical polymerization behavior was studied in acetone with dimethyl 2,2'-azobisisobutyrate (MIAB) as an initiator. The initial polymerization rate (R-P) at 60 degreesC was expressed by R-P = k[MIAB](0.6+/-0.1) [VTCA](1.0+/-0.1) where k is a rate constant. The overall activation energy of the polymerization was 112 kJ/mol. The number-average molecular weights of the resulting poly (VTCA)s (1.4-1.6 x 10(4)) were almost independent of the concentrations of the initiator and monomer, indicating chain transfer to the monomer. The chain-transfer constant to the monomer was estimated to be 9.6 x 10(-3) at 60 degreesC. According to the H-1 and C-13 NMR spectra of poly (VTCA), the radical polymerization of VTCA proceeded through normal vinyl addition and intramolecular transfer of the cyano group. The cyano group transfer became progressively more important with decreasing monomer concentration.