Of 60 amine cations tested in vitro for activity against Ceratocystis ulmi, that of methyl benzimidazol‐2‐ylcarbamate (carbendazim) showed the highest activity, this being constant with three different associated anions. Some guanidines, 2‐nitro‐morpholine and 2‐(thiazol‐4‐yl)benzimidazole (thiabendazole) showed considerable activity but a large group of alkylamines, 1‐methylalkylamines and poly‐amines were relatively inactive.