This study aims to investigate the contribution of diagnostic exposures to the 
rising rates of brain tumours and other neoplasms which are observed in several 
industrial nations. Included are benign tumours in the head and neck region and 
cataracts which are neglected in usual risk estimates by international and 
national radiation protection committees. Dose-effect relationships for tumours 
of the brain, skin, thyroid and other sites of the head region, leukaemia and 
cataracts are taken from the literature. Risk estimates are derived for 
paediatric head computed tomographies (CTs) as well as for brain tumours in 
adults. On the basis of estimates for Germany about the number of head scans, 
the annual rate of radiation-induced diseases is calculated. About 1000 annual 
paediatric CT investigations of the skull will lead to about three excess 
neoplasms in the head region, i.e. the probability of an induced late effect 
must be suspected in the range of some thousands. Additionally, a relevant 
increase of cataracts must be considered. The radiation-induced occurrence of 
meningiomas and other brain tumours most probably contributes to the 
continuously increasing incidence of these diseases which is observed in several 
industrial nations, as well as the exposure of the bone marrow by CT to the 
increase of childhood leukaemia.