This article is a report from an isolated community in a developing country. A case of acute psychosis with religious delusions caused a 'folie en masse' involving same twenty patients. Religious and cultural changes were significant causative factors. Two outbreaks were recorded. The first oase was treated succesfully. The second outbreak led to widespread disturbances and cases of manslaughter. Capital punisment of 3 patients seems to indicate the faillure of preventive psychiatric care.