Phenylurea herbicides such as linuron are commonly applied in agriculture. Common carp juveniles were subjected to 31.5 µg/L of linuron for 14 days, and then to 30 days of purification. Peripheral blood was sampled after 1, 3, 7 and 14 days of exposure and 7, 14 and 30 days of purification and hematological parameters were evaluated: erythrocyte (RBCc) and leukocyte (WBCc) counts, hematocrit (Ht), hemoglobin concentration (Hb), mean cell volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC) and differential leukocyte count. For evaluation of cortisol and catecholamine concentrations blood was sampled after 3, 6 and 12 h, after 1, 3 and 14 days of exposure, and after 30 days of purification. Linuron caused mainly transient increase in RBCc, Ht and MCV values and increase in WBCc and percentage of juvenile neutrophils. The herbicide caused persistant increase of cortisol and catecholamine concentrations. The results indicate that exposure to low concentration of linuron induced a stress response in common carp.