Toxoplasmosis is a widely distributed zoonosis produced by the parasite T gondii. In Chile the seroprevalence has been estimated between 20-37% in general population. Defined risk groups acquire or reactivate the infection by T gondii in patients undergoing SOT and HSCT are: heart transplant or heart-lung with D (+) and R (-), allogeneic HSCT with R (+), HSCT with cord cells, GVHD, history of previous clinical toxoplasmosis and use of corticosteroids for prolonged periods or in high doses. Hand washing, hygiene in food handling and weekly post-transplant surveillance since day 15 post transplant for six months, are universally recommended. All patients with SOT and HSCT, regardless of risk, should receive prophylaxis with cotrimoxazole and require no another specific prophylaxis against T gondii (A2). It is particularly important in high-risk patients who cannot receive cotrimoxazole prophylaxis establish specific alternative against T gondii (B3).