the invention relates to a method for the preparation of di - and polyamines of the diphenylmethane series from aniline and formaldehyde , care being taken during the start up that a sufficient excess of aniline with respect to formaldehyde is ensured , said excess amounting to at least 105 % of the desired molar ratio of aniline to formaldehyde for the target recipe of the mda to be produced .