AbstractStereoregular polymerizations of some vinyl ketones were examined by using several anionic catalysts.Methyl vinyl ketone was found to be polymerized by some catalysts such as calcium zinc tetraethyl and phenylmagnesium bromide (etherate) to give highly crystalline polymers which melt at about 160°C. and can easily form spherulites.Moreover, methyl vinyl ketone, unlike other vinyl compounds, was also polymerized to form crystalline polymers by use of triethylaluminum, diethylzinc and diethyleadmium as catalysts without any added co‐catalyst. The polymerization of methyl vinyl ketone with these metal alkyl catalysts was found to be anionic in nature from a series of copolymerization experiments.Phenyl vinyl ketone and methyl isopropenyl ketone were also polymerized by the same organometallic catalysts. Poly‐(phenyl vinyl ketone) obtained did not exhibit much higher crystallinity compared with the conventional polymer, whereas some specimens of poly‐(methyl isopropenyl ketone) prepared by the “at”‐complexes or diethylzinc as catalyst were highly crystalline.