Technical Abstract: Neospora caninum is a major cause of abortion in cattle but the reasons why some animals abort and not others remain unclear. The immunological control of the parasite in the placenta or by the foetus could be the key to determining the mechanism of abortion and/or transplacental transmission to the foetus. In this study, cytokine gene expression, analyzed by real time RT-PCR, at the maternal placenta (caruncle) and at the foetal placenta (cotyledon) of heifers infected at 110 days of gestation by intravenous inoculation of N. caninum tachyzoites was compared to the immune responses in those tissues from uninfected pregnant heifers. Animals were euthanized 3 weeks after infection. Up-regulated Th1, Th2 and regulatory expression was observed in both the maternal and the foetal placenta in the infected group. In the caruncle of infected animals the main changes of cytokine gene expression, included up-regulation of IFN-', IL-12p40, IL-6 and IL-10. In the cotyledon IFN-', IL-4 and IL-10 were up-regulated. The only cytokine that showed down-regulated expression in the infected group was TGF-ß in the cotyledon. The observed cytokine expression pattern was associated with alive but transplacentally infected foetuses suggesting that such cytokine pattern is beneficial to foetal survival, but could have a role in the transplacental transmission of the parasite.