Toxoplasma gondii has been reported to cause mortalities in marine mammals, including many cetaceans’ species. From 2001 to 2006, 36 Atlantic spotted dolphins (Stenella frontalis) stranded in Canary Islands have been necropsied. Tissue samples were fixed in 10% buffered formalin and embedded in paraffin, sectioned and stained whith Haematoxylin and Eosin for a routine light microscopical study. Three of these animals showed nonsuppurative necrotizing encephalitis associated to the presence of PAS positive toxoplama-like organism structures. Other organic lesions were identified in adrenal glands, skeletal muscle, heart or stomach where those organisms were also observed. Immunohistochemistry for detection of Toxoplasma gondii antigens was performed on the brain, adrenal gland, heart and lymphoid tissues. A disseminated toxoplasmosis was histopathological and immunohistochemically diagnosed. The presence of toxoplasmosis in marine mammals has been described in many species. In the present poster we contribute with 3 pathological cases of toxoplasmosis in Atlantic spotted dolphins, a protozoal disease not previously documented in this specie.