Interpretation of laboratory data is very important and based on comparison with reference intervals in routine practice. Leukocyte term includes all white blood cells and their precursors. These cells use blood circulation for going to the original tissues from their original locations. Total leukocyte count can be changed by various physiologic and pharmacologic reasons. In healthy cats, lymphocytes are the second most frequent leukocyte in the blood. Compared to middle-aged or old cats, young animals have higher absolute lymphocyte counts. The medical records of cats referred to the Ankara University Small Animal Hospitalfor general examination between April 2016 and August 2017 were retrospectively reviewed. Complete bloodcount (CBC) data includes red blood cell (RBC) count, haemoglobin, haematocrit (HCT), mean cell volume(MCV), mean cell haemoglobin (MCH), mean cell haemoglobin concentration (MCHC), red blood celldistribution width, platelet count, white blood cell (WBC) count, neutrophils, lymphocytes, monocytes,eosinophils and basophils.Of 5292 cats, 191 cats at the age between 0 and 1 and with CBC data were included in the study. CBCswere obtained from all 191 cats at the first visit. The relationship of hematological data to the reference range issummarized in Table 2. It was observed that 25.7% of the cats had leucocyte counts below the reference intervaland 3% had above the reference interval. Considering neutrophil counts, it is seen that 23.3% were lower and4.5% were higher. According to the results of 191 hemogram tests, lymphocyte counts of 39 cats (19.3%) andmonocyte counts of 9 cats (4,5%) were found to be low.This is a novel study that includes the results of detailed examination of breed and age distributionof complete blood count results at the first clinical visits of cats. According to our retrospective screening results,it is seen that the relation of monocyte numbers with age is statistically significant. (p = 0.018) The biggestdifference between the two age groups in the study is the pre- and post-adolescence periods. It is important toprecisely know the results of CBC test in the first visit to the clinic and to take the necessary precautions toeliminate the abnormal results before vaccination.