Abstract: A process for preparing 4-phenyl-1,3-dioxane from styrene and formaldehyde using a simplified method for working up the reaction mixture is disclosed, which comprises reacting styrene with an aqueous formaldehyde solution in the presence of an acidic catalyst at elevated temperatures, separating the aqueous phase from the organic phase and washing the latter with an alkaline aqueous solution to obtain a 4-phenyl-1,3-dioxane-containing product from which pure 4-phenyl-1,3-dioxane can easily be recovered, e.g., by means of distillation. The process can be further improved by adding a polymerization-inhibitor to the reaction mixture.