A reversed-phase HPLC method has been developed for the determination of vinylmagnesium chloride and vinylmagnesium bromide, based on the assay of 1-(9-anthryl)propen-2-ol, the product in the reaction between a vinylmagnesium halide and 9-anthraldehyde. The HPLC system with UV detection and an acetonitrile–water mobile phase containing phosphoric acid buffer was used for the separation and quantification of the reaction product after extraction. The method is selective for 1-(9-anthryl)propen-2-ol and linear response was established at 227 nm in the 0.002 to 0.5 mg ml^–1 concentration range. Vinylmagnesium halide concentration was calculated by using benzophenone as an external reference standard to standardize the response of authentic 1-(9-anthryl)propen-2-ol.