An outbreak of spontaneous Toxoplasma gondii infection on an Italian bird-farm is described. Small passerine birds (Serinus canaria, Carduelis chloris, Carduelis carduelis, Carduelis spinus, Carduelis cannabina, Pyrrhula pyrrhula) showed clinical signs consisting of anorexia, prostration, weight loss, diarrhoea and dyspnoea accompanied by a high mortality rate. Clinical, pathological, biological and serological investigations were performed. Characteristic lesions and Toxoplasma gondii specimens were identified in several tissues by histopathological examinations. The detection of antibodies against Toxoplasma gondii was constant in dead and sacrificed animals with macroscopic lesions. A therapy based on the administration of sulphadimethoxine and diaveridine was successful in limiting the mortality rate. Four months later some surviving birds developed ocular atrophy. Toxoplasma gondii cysts were observed in the brain and cerebral and ocular lesions described. Sera obtained from these animals were positive (>1:64) for antibodies against Toxoplasma gondii. The authors conclude with some observations on the spread of toxoplasmosis among cage birds.