Acute toxicity values of clove oil for carp were found 10 minLC50 74.3 mg/l; 10minLC0.1 51.6 mg/l; 10minLC99.9 110.1 mg/l; 96hLC50 18.10 mg/l; 96hLC0.1 15.45 mg/l; and 96hLC99.9 19.80 mg/l. The fish were divided into four groups for haematological and biochemical examinations of blood and histological examinations of tissues. The groups were Control I (before the anaesthetic administration), Experiment I (immediately after 10 min anaesthesia at the concentration of 30 mg/l), Experiment II (24 hrs after 10 min anaesthesia) and Control II (controls examined in parallel with Experiment II).