A process for making a 2-alkylbenzisothiazolinone which comprises reacting a bisamide of formula ##STR1## in water or an organic liquid containing water with a bisulphite or bisulphite release agent to form a Bunte salt and converting the Bunte salt under alkaline conditions to 2-alkyl-BIT. R is alkyl. Preferred substituents R are butyl, hexyl, 2-ethylbutyl and 2-ethylhexyl.