This study is designed to demonstrate the effectiveness of DermACELL in the treatment of chronic wounds of the lower extremities. DermACELL will be compared to conventional care in both subjects with diabetic foot ulcers (DFU) and subjects with venous stasis ulcers (VSU). In addition, DermACELL will be compared to an active comparator, GraftJacket, in subjects with diabetic foot ulcers.