Multicentre studies conducted in large general populations indicate that asthma is a disease extremely prevalent with up to 1 out of 10 adults and 1 out of 3 children who suffer from asthma worldwide. In spite of that, the control of asthma remains poorly documented in the general population. The prevalence of asthma is experiencing significant spatio-temporal variations that depend on exposure to environmental factors such as allergens (because of new conditions of exposure), parental smoking, air pollution and excess of hygiene. The latest data on temporal trends in the prevalence of asthma are in favour of stagnation or decrease of the number of asthmatics in high-income countries due to the cessation of environmental influences. Recently, several arguments are in favour of the involvement of host susceptibility in the development and worsening of asthma, which could contribute to explain temporal trends in asthma prevalence. Gene-environment interactions starting in early life using the epigenetic approach should be explored to better understand asthma epidemiological evolution.