Human and animal lung cells have been used successfully to model the toxic effects of inhaled sulphur mustard (HD). The epithelia of the upper respiratory tract are, however, the primary targets of inhaled HD. The aim of this study was to assess the potential of the mono- and di-isopropyl esters of glutathione (MIPE and DIPE respectively) as cytoprotectants in the human upper respiratory tract cell lines BEAS-2B and RPMI 2650. 2. The optimal concentrations for cytoprotection were shown to be 1.0 mg/ml for both DIPE and MIPE. Both compounds were found to protect cells by pretreatment, slightly less protection was observed in cells simultaneously exposed to sulphur mustard. The greatest protection was shown where MIPE or DIPE were in in situ at the time of exposure to HD. The optimum pre-treatment times were found to be 1 h for MIPE and 2 h for DIPE. Limited protection of cells treated with MIPE or DIPE immediately following HD exposure was also demonstrated. No protection was observed if MIPE or DIPE were not administered immediately following HD exposure. 3. Results suggest that MIPE and DIPE may be effective treatments for exposure to HD by inhalation.