The hepatoprotective activity of thymol, a terpenoid from essential oils of plant origin was investigated against paracetamol and CCl4-induced hepatic damage. The results showed that paracetamol produced 100% mortality at the dose of 1 g kg 1 in mice while pre-treatment of animals with thymol (150 mg kg-1) reduced the death rate to 30%. Oral administration of paracetamol (640 mg kg-1) produced liver damage in rats as manifested by the rise in serum enzyme levels of alkaline phosphatase (ALP) and transaminases (AST and ALT). Pre-treatment of rats with thymol (150 mg kg-1) prevented the paracetamol-induced rise in serum enzymes. The hepatotoxic dose of CCl4 (1.5 ml kg-1; orally) also raised the serum ALP, AST and ALT levels. The same dose of thymol (150 mg kg-1) was able to prevent the CCl4-induced rise in serum enzymes. The results indicated that thymol also prevented the CCl4-induced prolongation in pentobarbital sleeping time confirming hepatoprotectivity. It was concluded that thymol possesses anti-hepatotoxic activity.