Curcumin, an anti-inflammatory, antioxidant, was evaluated for its ability to suppress bleomycin (BLM)-induced pulmonary fibrosis in rats. A single intratracheal instillation of BLM (0.75 U 100(-1) g, sacrificed 3, 5, 7, 14 and 28 days post-BLM) resulted in significant increases in total cell numbers, total protein, and angiotensin-converting enzyme (ACE), and alkaline phosphatase (AKP) activities in bronchoalveolar lavage fluid. Animals with fibrosis had a significant increase in lung hydroxyproline content. Alveolar macrophages from BLM-administered rats elaborated significant increases in tumour necrosis factor (TNF)-alpha release, and superoxide and nitric oxide production in culture medium. Interestingly, oral administration of curcumin (300 mg kg(-1) 10 days before and daily thereafter throughout the experimental time period) inhibited BLM-induced increases in total cell counts and biomarkers of inflammatory responses in BALF. In addition, curcumin significantly reduced the total lung hydroxyproline in BLM rats. Furthermore, curcumin remarkably suppressed the BLM-induced alveolar macrophage production of TNF-alpha, superoxide and nitric oxide. These findings suggest curcumin as a potent anti-inflammatory and anti-fibrotic agent against BLM-induced pulmonary fibrosis in rats.