Menthyl vinyl ketone (MVK) was radically polymerized to obtain a polymer with excess of one-handed helical sense. Like as the anionically polymerized poly-MVK, the radically polymerized poly-MVK also kept stable one-handed helical conformation in solvent. The optical rotation and the circular dichroism signal intensity of the radically polymerized poly-MVK were larger than that of the anionically polymerized poly-MVK. The molecular weight of the radically polymerized poly-MVK was much larger than that of the THF-soluble part of the anionically polymerized poly-MVK. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 293-299, 2011