Two experiments were conducted separately with different concentration of dietary energy and protein to evaluate the performance, blood characteristics and bone mineral density (BMD) of broiler chicks. In experimentr 1, a total of 480 heads one-day-old Ross ${ imes}$ Ross broiler chicks were randomly divided into 6 treatments (5 replications; 16 birds/pen). Three concentration of ME (3,000, 3,100 and 3,200 kcal/kg) and two of CP (pre-starter 22, 23%, starter 20, 21% and finisher 18, 19%) in a $3{ imes}2$ factorial arrangement of treatments were used. In experiment 2, similar chicks and CP concentration was used but ME concentration was changed (pre-starter; 3,000, 3,050 and 3,100 kcal/kg, starter; 3,050, 3,100 and 3,150 kcal/kg, finisher; 3,100, 3,150 and 3,200 kcal/kg) in the diet. In both experiments, 10 blood and tibia samples were collected per treatment and blood characteristics and BMD were analyzed. In experiment 1, weight gain and feed intake were increased by the 3,000 kcal/kg ME in the diet (P<0.05). Serum total protein and albumin levels were increased numerically with the level of CP in the diet. Total cholesterol and HDL content were increased numerically with the energy content in the diet. Consistently in experiment 2, weight gain was increased numerically by the energy and protein level (prestarter $3,000{ imes}23$, starter $3,050{ imes}21$ and finisher 3,100 kcal/kg ME and 19% CP) in the diet. Serum glucose level was increased with the energy level in the diet (P<0.05). Therefore, serum total protein, albumin, triglycerides, total cholesterol and HDL contents were tended to increase with the energy increments in the diet.