Antimicrobial compounds have been used for decades in poultry diets to increase performance and decrease morbidity particularly in broiler chickens. However, consumer pressure related to the potential development of antibiotic-resistant bacteria has resulted in the development of non-antibiotic feed additives that may also improve broiler erformance. In recent years, aromatic plants and their extracts have received attention as growth and health promoters. Such products have several advantages over commonly used commercial antibiotics since they are residue free and they are also, generally recognized as safe and commonly used items in the food industry. The antimicrobial properties of medical plants and their extracts have been widely reported because they consist of many active ompounds such as carvacrol, eugenol,which partition lipids in the bacterial cell wall and mitochondria, disturbing the structures and rendering them more permeable. Generally,medical plants are slightly more active against Gram-positive than Gramnegative bacteria. Medical plants are well known for their antioxidant activity and show a considerable effect on increasing the antioxidant capacity of chicken meat because they consist of many of active compounds such as tocopherol, carvacrol. Spices or their active principles have been reported to stimulate digestive secretions such as lipase, amylase and proteases.because they consist of many active compounds such as anothol, eugenol. Variable effects of medical plants and their extracts on the productive performance of broiler have been reported. The majority of experimental results indicate improved body weight gain or final body weight and feed conversion ratio.