There is an increasing awareness that also growth in FEV1 may be of importance to development of chronic obstructive lung disease in later life. This paper reviews current knowledge on factors in foetal and childhood life that may reduce lung growth. Passive smoking as well as malnutrition in foetal life is related to impaired lung function in later life. Birth weight is a risk factor to lung growth independent of gestational age and maternal smoking. Active and passive smoking in childhood and adolescence reduces growth. Girls seem to be more vulnerable than boys to the effect of smoking. Also host characteristics like atopy, bronchial hyper responsiveness and asthma are related to impaired growth of FEV1. Lower respiratory tract infections before the age of seven are also related to impaired lung growth in adult life. Although several studies have found socioeconomic status among adults related to chronic obstructive lung disease, it is not known to what extent low socioeconomic status affects growth of lung function after adjusting for risk factors like active and passive smoking and lower respiratory tract infections. Normal lung growth varies with age and between male and female. The importance of the various risk factors may differ depending at what point in the lung growth they come into play. Limited data is available about the interrelationship between the risk factors and the mechanisms through which they work.