Tumour necrosis factor alpha (TNF-alpha) is a cytokine that is secreted by activated macrophages and monocytes. This work studied TNF-alpha level in sera of patients with toxoplasmosis. Twenty eight female patients (12 of whom had obstetric troubles) and 17 healthy controls were the subjects in this work. According to IHA test and detection of IgM antibodies, three groups of patients were defined, group (I) patients with acute infection, group (II) patients with chronic infection and had high antibody titre, group (III) patients with chronic infections and had low antibody titre. Sera from patients as well as controls were tested for their level of immunologically reactive TNF-alpha using enzyme-linked immunosorbant assay (ELISA). TNF-alpha levels in the sera of patients were significantly higher as compared to healthy control group. Acute infection was associated with the highest levels of TNF-alpha indicating that it may play a role in the pathogenesis of acute toxoplasmosis. In chronic infection, the level of TNF-alpha correlated with IHA antibody titre suggesting that, antibodies against T. gondii may participate in TNF-alpha production. It could be concluded that TNF-alpha may contribute to the pathology in acute infection and may play a role in modulating the host's immune defence against T. gondii in chronic infections.