In previous reports, it was indicated that measurement of activity of Interferon-tau Stimulated Genes (ISGs) in Peripheral Blood Leucocytes (PBLs) may be used as an alternative early pregnancy detection method in dairy cows. However, there are no data showing the expression profiles of ISGs in other body fluids containing leucocytes such as milk. In the present study, it was hypothesized that leucocytes in milk samples may reflect the increases in expression profiles of ISGs as shown in PBLs. For this purpose, nine pregnant lactating Holstein cows were used. Insemination day was accepted as day zero (day 0). Blood and milk samples were collected on day 0 and 18 after insemination for cell isolation. Total RNA was extracted from isolated cells and converted to cDNA. Steady state levels of Interferon-tau Stimulated Gene 15 (ISG15), Myxovirus (influenza virus) resistance 1 (MX1) and 2 (MX2) mRNA transcripts were assayed by using real-time reverse transcriptase PCR. Relative Expression Software Tool (REST2009) was used for statistical analyses. There was no statistical significant difference for expression levels of ISG15, MX1 and MX2 mRNAs between days 0 and 18 in milk samples. However, when compared to day 0, levels of ISG15 and MX2 transcripts were increased 6.97 +/- 0.68 fold and 5.84 +/- 1.27 fold on day 18 in PBLs in pregnant cows, respectively (P<0.05). According to this result, it may be suggested that milk cells are not suitable measurement of expression profiles of ISGs to detect early pregnancy in lactating dairy cows.