A process for the preparation of a pulverulent organomagnesium compound involves bringing together into intimate admixture a particulate hydroxyl functional material with an organomagnesium-containing material. The process is conducted at a temperature below the melting point of the hydroxyl functional material but at a temperature sufficient to convert at least a portion of the hydroxyl functional material to the pulverulent organomagnesium compound. The aforesaid organomagnesium compounds are useful as intermediates in generating anionic sites for anionic polymerization.