Certain 2-anilino-4H-3,1-benzothiazines of the formula: ##STR1## wherein R.sub.1 is hydrogen and R.sub.2 is 4-dimethylamino, 5-chloro-2,4-dimethoxy or 3,4-dichloro; and R.sub.1 is chloro and R.sub.2 is 4-acetyl or 3-chloro are effective anthelmintic agents.