The present invention relates to a process for distilling an aqueous polymethylol mixture which comprises a polymethylol of the formula (I) (HOCH2)2—C—R2  (I) in which each R is independently a further methylol group or an alkyl group having 1 to 22 carbon atoms or an aryl or aralkyl group having 6 to 22 carbon atoms, a tertiary amine, water and the adduct of tertiary amine and formic acid (amine formate), which comprises performing the distillation in a distillation column which is connected at the bottom to an evaporator, the bottom temperature being above the evaporation temperature of the monoester of formic acid and polymethylol (polymethylol formate) which forms during distillation. The present invention further relates to a composition comprising polymethylol and 1 to 10 000 ppm by weight of polymethylol formate, and to the use thereof.