Abstract: A process is provided for the production of a monohydroxy monocyclic acetal, e.g., trimethylolpropane cyclic formal, of a trihydroxy alcohol, e.g., trimethylolpropane, and an aldehyde, e.g., formaldehyde, by subjecting a "heavier condensation product" of the trihydroxy alcohol and the aldehyde than the desired cyclic acetal, i.e., one having a higher molecular weight and boiling point, to acetal formation conditions. In a preferred embodiment, the product of reaction of the trihydroxy alcohol and aldehyde is treated to remove the desired monohydroxy monocyclic acetal product and at least part of the remainder comprising the heavier condensation product is recycled to the reaction together with a flesh supply of trihydroxy alcohol and aldehyde. The monohydroxy monocyclic acetal product may be further reacted to obtain a desired ester, e.g. trimethylolpropane cyclic formal acrylate, such as by transesterifying the acetal with a low boiling ester of the esterifying acid, e.g.