The experiment was conducted to determine the individual and combined effects of oregano and garlic essential oils on performance, carcase, organ and blood characteristics and intestinal microflora of broilers. Four starter and grower diets were formulated to provide a similar nutrient profile with the exception of using two feed additives or a combined addition of these additives. The diets were supplemented with: no essential oil (control), oregano essential oil at 300 mg/kg, garlic essential oil at 300 mg/kg and oregano essential oil at 150 mg/kg + garlic essential oil at 150 mg/kg. All chicks were fed starter diets from 0 to 21 days of age and experimental grower diets from 21 to 42 days of age. Body weights of broilers at 42 days were not affected by garlic oil and both essential oil combinations; however, oregano essential oil supplementation significantly decreased body weights. There were no differences in feed intake and feed conversion efficiency. Carcase yields and relative weights of proventriculus, gizzard, duodenum, jejunum, ileum, colon, cecum liver, pancreas, spleen, heart and bursa, the concentrations of serum cholesterol, triglicerid and viscosity, Total organism, Streptococcus, Lactobacillus spp., and Coliform counts in the ileum were not affected by treatments. Clostridium counts were significantly decreased in birds from oregano oil, garlic oil and oregano oil + garlic oil compared with that of birds from control. (C) 2010 Elsevier B.V. All rights reserved.