A method is disclosed for the production of pentaerythritol diphosphites of high spiro isomer content. The pentaerythritol diphosphites are produced via sequential transesterification of pentaerythritol with a monophosphite followed by a substituted phenol or other alcohol, wherein the transesterification reactions are carried out under controlled conditions of temperature and pressure. The unique reaction conditions result in intermediate and final pentaerythritol diphosphites of high spiro isomer content and high total yield of the diphosphites.