We have previously reported the clinical course of a patient poisoned with paraquat who was treated with whole lung irradiation and who survived severe pulmonary damage. Four further cases are reported who were much more severely poisoned and who died despite early pulmonary irradiation. There is no definite evidence that this or any other form of cytotoxic therapy can influence the course of paraquat lung. As there is no adequate laboratory model, further investigation of such therapy should be in the context of a prospective clinical trial. Treatment of only one lung would allow rapid identification of a therapeutic effect of irradiation.