The present invention relates to the use of pyridin-4-ylmethyl sulfonamides of formula (I) (I) wherein R
a
, n, A, Y and D are as defined in the claims and the N-oxides and the salts thereof for combating phytopathogenic harmful fungi, and and to compositions and seeds comprising at least one such compound. The invention also relates to to novel substituted sulfonic acid amide compounds and processes for preparing these compounds.