Cases of poisoning have increased considerably in Brazil, however for state of Piauí only two studies were carried out so far. Here, we investigated, through the notification forms, the epidemiological characteristics of cases of poisoning that occurred during 11 years in a macro-region of Picos, state of Piauí, Northeastern Brazil. Furthermore, we also check whether the species recorded in the notification forms correspond to the species that occur in the region. We recorded 1.249 cases of envenomations, being 41% caused by scorpions, 35% caused by snakes and 24% caused by spiders. Most cases (arachnids = 99%, scorpions = 93%, snakes = 52%) there was no identification of species causing the accident. Most of the victims of the accidents (66%) were male individuals between 18 and 24 years from rural areas, stung during field activities in the rainy season (January-March). The most common injury sites were the lower limbs (37%) and the majority (53%) of the accidents was the mild type. This is the first study that reports the epidemiological profile of a series of envenomations (including arachnids and snakes) during 11 years of records in the state of Piauí. Furthermore, we also present the first list of species of arachnids and snakes of medical importance to the state. Our results demonstrate that there was a high incidence of accidents by venomous animals in the Center-South region of the state, most of the records was not notified in SINAN, most records does not present the identification of the species responsible for the accident, and there are records whose species was incorrectly identified.