3-Methylene-6-methyl-1,5-dithiacyclooctane (MDTO, 1) was polymerized in both the presence and absence of a number of chain transfer agents, viz. 1-butanethiol (BuSH), dibutyl disulfide (BuSSBu), and dibutyl sulfide (BuSBu). Mark−Houwink−Sakurada (MHS) constants for poly(MDTO) were found to be K = 23 × 10-5 dL g-1 and α = 0.67. Using these parameters, chain transfer constants were obtained at 60 °C and are reported as 0.13 (BuSH), 0.19 (BuSSBu), and 0.0025 (BuSBu). These values are compared to the corresponding chain transfer constants obtained for styrene (STY) and methyl methacrylate (MMA). Subsequently, the chain transfer activity was measured over a range of temperatures (40−80 °C), and Arrhenius parameters were determined. Significant differences in chain transfer activity between carbon- and sulfur-centered radicals were observed. In addition, the extent of transfer to monomer was determined across the range of temperatures 40−100 °C, yielding a value for CM of 55 × 10-4 at 60 °C. The likely extent o...