Abstract: Measurement of haematological parameters provides valuable information for evaluation of health status of man and animals, but due to lack of reference values for avian blood profiles, it is not widely used in poultry. This study has contributed to the current knowledge on avian blood profiles, or more specifically demonstrated leukograms and haemograms of four main broiler strains (Ross, Cobb, Arbor-Acres, and Arian) during 8 weeks husbandry period. Blood samples were collected from chickens at different age (1 to 56 days old) with 7-day sampling intervals. Total numbers of RBC and WBC, PCV, Hb, MCV, MCH, MCHC, ESR, together with absolute count of heterophils, lymphocytes, monocytes, eosinophils, and basophils as well as H / L ratio were determined. One-way ANOVA, Wilcoxon, Spearman correlation and Kruskal-Wallis H tests from SPSS11 were used for statistical analysis of the results. This study showed that age affects significantly (P< 0.05) the haematological profiles of the broiler strains. With increasing of age, the erythrocytic parameters (except MCV, MCH, and MCHC) and leukocytic parameters (except heterophils and H / L ratio) were significantly increased (P< 0.01), but MCV, MCH and absolute count of heterophils as well as H / L ratio were significantly decreased (P< 0.01).