One of the main objectives of SIDRIA-2 study was to evaluate the possible changes in the occurrence of social characteristics and risk factors for asthma and allergies in childhood, comparing the data obtained in 2002 to those collected in 1994-1995. A positive change in socio-economic characteristics of the childrens' and adolescents' families was generally observed. The levels of exposure to outdoor (traffic) and indoor (passive smoking) pollutants are still high, although a decreasing trend in parents' smoking habits is evident.