A series of 3, 4-dihydro-3-oxo-2H-1, 2, 4-benzothiadiazine-1, 1, dioxides with cytotoxic activity against human solid tumors is described. Synthesized compounds showed mild but broad spectrum cytotoxicity in vitro. The lipophilic substituents like alkyl, alkoxy and chloro on benzene ring increased the activity. Also hydrophobic group on 3 or 4 position of benzothiadiazine was important for the activity.