In recent years, there has been a massive trend in Ukraine to keep cats, which has inevitably led to an increase in the incidence of their diseases. In the general pathology of cats, viral diseases occupy a leading place, and of particular concern is calicivirosis, which is caused by a virus capable of high mutation rates and can cause atypical course with nonspecific manifestations of clinical signs. Therefore, given the urgency of this issue, the result of our research is to clarify, supplement and summarize data on hematological and biochemical parameters of blood and erythrocytopoiesis in calicivirosis in cats, because blood is a sensitive and informative indicator of the body, responds quickly to changes as exogenous. and endogenous factors. The research was conducted in veterinary clinics of Zhytomyr and Kyiv, on purebred and outbred cats (n = 18). Diagnostic studies to confirm feline calicevirus were performed using rapid tests Ag Test (FCV Ag), Quicking Biotech Co., Ltd. and ELISA and PCR for the presence of calicivirus antigen on the basis of a private veterinary laboratory LLC "Bald" in Kiev.
 Comprehensive studies have shown that cats with calicivirosis (18) are characterized by changes in morphological and biochemical composition of blood. Deviations from physiological limits were found, namely erythrocytopenia P≤0.05, thrombocytosis P≤0.05, leukocytosis P≤0.05, monocytosis P≤0.01, increase in ESR P≤0.001 and lymphocytopenia P≤0.05, for biochemical ones it is a significant increase in the concentration of globulin P≤0.001, creatinine P≤0.001, urea P≤0.05 hyperenzymemia α-amylase P≤0.001, and ALT P≤0.05. As a result of experimental research of morphological indicators of blood the difficult pathogenesis of a disease with multiorgan insufficiency is established.