An ortho-mercaptoaniline derivative having the general formula
wherein X is (H,H) or O; n is 1 or 2; and
R1 is (C1-C6)alkyl or phenyl-(C1-C6)alkylene, optionally substituted at phenyl with a (C1-C6)alkyloxy group;
R2 is (C1-C6)alkyl or (C1-C6)alkyloxymethyl;
R3 is hydrogen or methyl, with the proviso that R3 is hydrogen if R1 is methyl;
and acid addition salts thereof;
a process for the preparation of such a compound, and a pharmaceutical composition comprising such a compound for anti-amoebal action or the treatment of dysentery.