Effects of starvation and malnutrition on peripheral blood parameters, composition and activity of haematopoietic tissue and oxygen consumption rate were evaluated in common carp. Fish were fed Aller Aqua Classic (control diet), ground barley (diet of low nutritional value) or starved for 15 weeks. Blood was analysed after 3, 7 and 15 weeks. At the end of the experiment, oxygen consumption rate of fish was measured and head kidneys were isolated. Values of most peripheral blood parameters did not significantly differ among experimental groups but erythroblast frequency was reduced in starved fish. Haematopoietic tissue of control fish contained significantly lower percentage of early blast cells and erythroid cells compared to the other groups. Neutrophilic lineage was the least frequent in starved fish, and the most abundant in the control. Frequency of lymphoid, monocytoid and thrombocytoid cells did not significantly differ among experimental groups. The control fish showed significantly higher haematopoietic activity (ratio of proliferating to apoptotic cells) compared to the other groups. Control fish showed the highest oxygen consumption rate and starved fishthe lowest. Starvation or low-quality feeding did not cause anaemia or significant immunodeficiency in carp but reduced haematopoietic activity, which was directly related to the metabolic rate.