Toxoplasma gondii is an obligate intracellular parasite that infects 10-20% of the overall population in the US with rates increasing with age. T. gondii infects most warm blooded animals where an antibody response is generated to control the infection, however, the parasite forms bradyzoite cysts in brain and muscle. It can only reproduce in felines where oocytes are excreted in the feces. Infection can occur by a variety of routes. In cats, infection occurs by eating infected prey, primarily rodents or birds. Infection in humans can occur by eating undercooked infected meat, handling infected cat feces, ingesting oocytes on unwashed fruits or vegetables, or drinking contaminated water. Another important route of infection is congenital infection. This book discusses the potential risks this parasitic infection may cause. It also reviews the parasite's life cycle.