A WHO expert group recommends neonatal screening for alpha1-antitrypsin deficiency (alpha1ATD). Homozygous alpha1ATD PiZZ occurs in 1 in 5000 of the U.S. Caucasian population and up to 1 in 500 individuals of the European population, with a large regional variation. It is a risk factor that predisposes mainly to liver disease in early infancy and emphysema in early adulthood. Most importantly, smoking decreases the duration of the asymptomatic phase and life expectancy by 10-20 y. The Swedish alpha1AT screening programme and subsequent information and advice prevented the majority of adolescents from starting to smoke. The involved parents and alpha1ATD adolescents retrospectively recommended neonatal screening. Potential advantages of neonatal alpha1AT screening are: early diagnosis and treatment of neonatal liver disease, optimal treatment of fever and bacterial infections theoretically preventing liver cell damage, genetic advice and information about the consequences of passive and active smoking. Potential advantages of postponing screening until age 11-12y are: identification of alpha1ATD close to the age when smoking may start, and possibility for the child to take part in the screening decision. Disadvantages of alpha1AT screening are: psychosocial reactions--the mother probably being most vulnerable in the neonatal period--and discrimination by insurance companies and employers. Important uncertainties are: lack of knowledge concerning participation in a voluntary alpha1AT screening, psychosocial reactions and the efficacy of anti-smoking advice if the information is given to school-age children and families. Thus the question whether and when to screen for alpha1ATD is still the topic of lively debate.