Several parameters of in vitro culturing were investigated for two kinds of human macrophages cell fractions, i.e. sorted by flow cytometry and not sorted, as follows:--growth ability during serial in vitro passages, and--percent rate of CD13, CD14 and CD33 expression at different in vitro passage levels. Results point out the ability of sorted cells to survive to a higher number of serial passages. A dramatical loss of CD13 and especially CD33 markers was noticed during culturing within the not sorted cells, as compared to homologous sorted ones.