The recent study was conducted to investigate the effects of 0 (control), 0.2, 0.4 and 0.6% alcoholic extract of thymuse vulgarise in drinking water on immune response of broiler chickens. One hundred and sixty day old chicks (Ross 308) in four treatment and 4 replicate each based on a completely randomized design were used. Immune organs relative weight such as spleen and bursa fabriciuse not affected by using of thyme extract at 21 and 42 days of experimental period but higher bronchitis antibody titer for the birds consumed 0.2 and 0.6% of thymuse vulgarise showed (P<0.05) as compared with those consumed the 0.4% thymuse vulgarise extract and control birds at 21 days of age. Moreover, consumption of thymuse vulgarise extract in water increased the bronchitis antibody titer as compared to the control birds in orthogonal comparsions. But there were no significant differences between the treatments for bronchitis antibody titer at 42 days of age and Newcastle antibody titer at 21 and 42 days of age.
