Abstract: According to the present invention there are provided isothiuronium salts of the general Formula I ##STR1## wherein R.sup.1 is C.sub.1-6 alkyl, C.sub.2-6 alkenyl, C.sub.2-6 alkynyl, C.sub.3-6 cycloalkyl, aralkyl or aryl, the said groups being optionally substituted by one or more hydroxy, mercapto and/or halogen;R.sup.2 stands for hydrogen, C.sub.1-6 alkyl, C.sub.2-6 alkenyl, C.sub.2-6 alkynyl or C.sub.3-6 cycloalkyl;X represents an organic or inorganic anion/.The compounds and salts of the present invention can be prepared by reacting a compound of the general Formula II ##STR2## with an agent capable of introducing a R.sup.1 group. The compounds of the general Formula I exhibit antitumor and immunostimulant effect and are useful in therapy.