Propagation rate coefficients (k(p)) for the free-radical polymerization of dodecyl methacrylate (DMA) in solution in toluene have been measured via electron spin resonance (ESR) spectroscopy in the temperature range 0 to 50 degrees C. The polymerization is photochemically induced at different initiator concentrations of di-tert-butyl peroxide (DTBP). Free-radical concentration under steady-state conditions is deduced from double integration of the well-resolved ESR spectra, consisting of 13 lines in the initial period of the polymerization reaction and 9 lines at enhanced degrees of monomer conversion. The hp values from ESR analysis are in excellent agreement with the corresponding data from pulsed laser polymerization (PLP)/size-exclusion chromatography (SEC), the IUPAC-recommended procedure for reliable k(p) measurement. The activation energy associated with the ESR k(p) data, E-A = 21.7 +/- 2.0 kJ mol(-1), is in full agreement with E-A (k(p)) results from recent PLP-SEC studies.