The aim of the study was to compare the absolute and relative monocyte count obtained by microscopic method (M), flow cytometry (FC) and the automated hematological analyzers (HA) as well as to validate of reference ranges of monocytes count in polish population. Blood samples from 84 healthy adults were analyzed. The cell counts determined by three HA: two HMX and one Cell-Dyn were confronted with M and FC. The counts exceeding 800/ul were found in 4.8%, 5.9%, 15.5% and 13.1% patient&#8217;s blood samples assessed by: M, FC, HMx and Cell-Dyn, respectively. The difference between both HA and M was significant (p<0.05). FC detection of relative count provided the closest results to M but difference between the means was significant. The staining anti CD45 and anti CD14 monoclonal antibodies gives the best agreement with the both HA than with M. All examined methods revealed significant percentage of monocytes above the upper limit of the reference range accepted as 8%. Our preliminary data indicate that the upper limit of the reference range of monocytes should be higher. There is a great need for cross-sectional population study to establish new reference range for monocytes in order to appropriately manage individuals with infection diseases and hematological disturbances.