Toxoplasmosis is the name of an infectious disease and the causative agent is toxoplasma gondii parasite. This parasite had been discovered in 1908. It's seen worldwide and course of disease in immunocompetent individuals is generally asymptomatic. The seropositivity rates in Turkey are between 30 and 79 percent. Parasite completes its sexual life cycle in the feline's gastrointestinal system and can infect many mammals including humans in its asexual life cycle. Humans can acquire the disease via digestion of infected meals. Other possible ways of transmission are transfusions from infected blood products and transplacental way from infected mother to fetus. When the disease becomes symptomatic; lymphadenopathy, rashes, hepatosplenomegaly, fever may be seen and especially the immunosupressive individuals can experience the mortal complications such as encephalopathy, pneumoniae, pericarditis. If the mother has active disease during her pregnancy period, the parasite can be transmitted to the fetus via plasental way and stillbirth can be seen, or it can cause conditions like chorioretinitis, hydrocephalus, mental retardation. Testing for IgM and IgG via the ELISA is the most common method for diagnosis. The Avidity test, Sabin-Feldman dye test, PCR, latex aglutination and histopathology methods may be useful for supporting the diagnosis or making definitive diagnosis. The primer agents for treatment are pyrimethamine and sulfadiazine. Clindamycin, TMP-SXT, azithromycin and the atovaquone are the alternative agents for the therapy. Spiramycin is used in pregnant women for the protection of fetus from infection.