Bleomycin (BLM) induces lung injury and fibrosis in the murine lung and enhances tumor necrosis factor (TNF)- and collagen mRNA expression in the murine lung. Amifostine is a cytoprotective agent that protects normal tissues from the cytotoxic effects of chemo- and radiation therapy. We investigated the effect of amifostine in BLM-induced lung injury in mice. Mice received intraperitoneal amifostine (200 mg/kg) 30 min before and/or 1, 3, and 7 days after an intratracheal injection of saline or BLM (4 U/kg). The animals were killed 14 days after BLM exposure, and their lungs were studied for TNF- and collagen mRNA expression, hydroxyproline content, and histopathology. Light microscopy demonstrated that amifostine exacerbated the BLM-induced lung injury in mice. Increased TNF- mRNA expression as a result of BLM exposure was not modulated by amifostine treatment. In contrast, amifostine treatment enhanced the BLM-induced expression of ₁(I) procollagen mRNA in the lung. Similarly, mice treated with amifostine before BLM exposure accumulated significantly higher amounts of hydroxyproline (111 ± 5 µg/lung) than BLM-treated animals (90 ± 6 µg/lung). These data suggest that amifostine treatment exacerbates BLM-induced lung injury in mice.