Abstract: The invention relates to a process for preparing essentially formic acid-free N-alkyl-N′-methylalkyleneureas of the formula with R1=H or CH3, R2=CnH2n+1 with n=1-4 and x=0 or 1, from the corresponding alkyleneureas by reaction with monomeric or polymerized formaldehyde in the presence of formic acid. This entails feeding the mixture, obtained in the reaction, of N-alkyl-N′-methylalkyleneurea and formic acid to the upper region of a distillation column, distilling without further additions and removing essentially formic acid-free N-alkyl-N′-methylalkyleneurea in the lower region of the column.