A process for the preparation of arylidene dyes comprises the reaction of an aromatic amine with an enolate salt of a formylated active methylene compound in the presence of a sulfonyl halide compound. An enol sulfonate is postulated as a reactive intermediate in the reaction. The process gives high yields of products under mild reaction conditions and allows the use of aromatic groups containing substituents such as hydroxy that lead to side reactions and low product yields with previously known methods for making arylidene dyes.