Amifostine (S-2[3-aminopropylamino]ethyl phosphorothioate) and one of its analogues, DRDE-07 (S-2[2-aminoethylamino]ethyl phenyl sulphide) are promising prophylactic agents for sulphur mustard (SM; a blistering agent) toxicity. When given orally, DRDE-07 was more effective than amifostine as a prophylactic agent against SM administered percutaneously. Various pharmacological and toxicological studies are required before the introduction of a chemical as a drug. The respiratory effects of amifostine and DRDE-07 were carried out in rats using a body plethysmograph fitted with a volumetric pressure transducer for sensing the respiratory flow signals. The signals were amplified, digitised, and stored on a personal computer for further analysis. After taking control recordings of respiratory signals, different doses (0.5 LD 50 , 1.0 LD 50 and 2.0 LD 50 ) of amifostine and DRDE-07 were administered orally (LD 50 amifostine = 2262 mg/ kg; DRDE-07 = 1599 mg/kg), and the respiratory changes were monitored for 4 h. Amifostine and DRDE-07 showed a uniform breathing pattern even in 2.0 LD 50 dose. However, a significant dosedependent decrease in respiratory frequency was observed following amifostine administration. DRDE-07 did not show any significant change. The tidal volume was not altered significantly both in amifostine and DRDE-07 administered animals. The study shows that DRDE-07, even in lethal doses, may not affect the respiration immediately, whereas, amifostine may decrease the respiratory frequency.