The typical computer tomographic signs of ischaemic cerebral infarct are discussed on the basis of 631 cases. Infarcts have three typical stages. Stage I, one week, fresh infarct with signs of oedema (space-occupying lesion with an unsharp margin, slightly reduced density, lack of contrast uptake). Stage II, second to fourth week, reduction in the oedema. Frequently very marked contrast enhancement of the cortex and basal nuclei. Stage III, later than four weeks. Development of malacic cysts, with further reduction in density and size. Development of homolateral atrophy. The computer tomographic diagnosis of cerebral infarcts during Stage I is often very difficult. Distinction from infiltrating tumour is often possible only after further observation. The diagnosis of cerebral infarcts in stages II and III is possible in most cases. Haemorrhagic cerebral infarcts do not follow a temporal pattern as accurately as anaemic infarcts. They show circular increase in contrast of slowly diminishing size. The increased contrast persists considerably longer and is clearly distinguished from that in an anaemic cerebral infarct.