Fernando de Noronha Island, because of its ecological characteristics, has virtually no atmospherical pollution that could cause asthma. Nevertheless, asthma prevalence in children younger than 6 years old is 11.22%. 17 asthmatic children and 68 healthy ones were included in this case control study (1:4 case/controls) conducted in a closed community free from atmosphere pollution. Maternal asthma and exposure to smoking were more frequently associated with asthmatic children than with controls, the risc of asthmatic syndrome being respectively 6.9 and 4.6 times bigger. As for breastfeeding no protective effect was found in both cases and controls.