derivatives of 2 - 6 - nitrobenzoic acids are disclosed , wherein at least one of the sulfamyl substituents is selected from amino -, - amino -, or di - amino -, hydrogen , lower alkyl , hydroxy -, allyl , or when taken together with the nitrogen of the sulfamyl moiety , form a heterocyclic ring . these compounds have activity in increasing the sensitivity of hypoxic tumor cells to therapeutic radiation . also disclosed are methods of preparing such compounds and pharmaceutical compositions including such compounds .