Aim: We aimed to investigate the activity of ADA isoenzymes in serum of rats with lung contusion Material and Method: Lung contusion was induced in twelve male wistar albino rats by dropping a cylindrical weight from a height of 50 cm with a mobile platform positioned over the thorax. Rats were killed at 24 hour (n= 6) and 72 hour (n= 6) after contusion. ADA isoenzymes were measured in serum traumatic and control (n= 6) (uninjured) rats. Results: Our results indicated that serum total ADA activities were significantly decreased at 72 h after contusion. There was a significant decreased in ADA1 activity at 24 and 72 h after contusion when compared with controls. On the other hand, the increase in the ADA2 activity at 24 h and 72 h was not statistically significant. Discussion: In conclusion, serum ADA2 became predominant isozyme because of the inflammatory response in the lung contusion. However, further studies are needed to elucidate the regulatory mechanisms that effect the activity of serum ADA1.