Aim: The aim of the study was to evaluate anti inflammatory activity of aqueous extract of Boerhaavia diffusa leaves. Material & Methods: The anti inflammatory activity was evaluated by carrageenan induced rat paw edema to determine the activity on acute inflammation and cotton pellet induced granuloma to determine activity on sub acute inflammation. Rats were divided into 4 groups, 6 rats in each group. Group I (control) received 0.1ml of 4% gum acacia, Group II & III (test) received Boerhaavia diffusa extract at doses of 200mg/kg and 400mg/kg bodyweight, Group IV (standard) received Diclofenac 10mg/kg bodyweight, all the above drugs were administered one hour prior to sub plantar injection of 0.1ml of 1% carrageenan. Anti inflammatory activity was estimated by measuring paw volume before and 1 hr, 2 hr, 3 hr and 4hr after carrageenan administration and percentage inhibition was calculated. To determine activity on sub acute inflammation, Cotton pellet granuloma model was used. The animals were divided and treated same as in acute inflammation model for seven consecutive days. On eighth day the implanted cotton pellets were removed, dried and weighed. The percentage inhibition of granuloma formation was calculated. Results: Boerhaavia diffusa aqueous leaves extract treated groups with 200mg/kg and 400mg/kg bodyweight exhibited dose dependent and significant antiinflammatory activity in acute (carrageenan-induced rat paw edema) and sub acute inflammation (cotton pellet induced granuloma). Conclusion: Boerhaavia diffuse extract showed significant anti inflammatory action in acute & sub acute experimental models and the activity was dose dependent.