The invention provides fungicidal compositions containing phosphonium salts of formula:- in which n represents 0, 1, 2 or 3, R represents a halogen atom or an optionally substituted alkyl, haloalkyl, alkoxy or haloalkyl group, R¹, R² and R³ independently represent an optionally substituted alkyl, cycloalkyl, phenyl or benzyl group and X represents an anion; certain novel phosphonium salts, a process for the preparation of such compounds and a method of combating plant pathogenic fungi using such compositions or compounds.