A complete assessment of late effects of X-ray diagnostics should take into 
account that radiation sensitivity varies considerably for the different ages at 
exposure and, furthermore, that not only malignant diseases but also benign 
neoplasms are induced which also may lead to severe detriment of the patient. 
Risk estimates are derived for paediatric head CTs as well as for brain tumours 
in adults. 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. On the basis of estimates for Germany about the number of head 
scans, the annual rate of radiation-induced diseases is calculated. 1,000 annual 
paediatric CT investigations of the skull will lead to about 3 excess neoplasms 
in the head region, i.e., the probability of an induced late effect must be 
suspected in the range of some thousandths. 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.