The diagnosis of DAI is not always easy, and should be based on adequate sampling of appropriate anatomical areas from a sliced, fixed brain. It is now recognised that there is a continuum of traumatic white matter damage, and that DAI represents only the severe end of the scale. Such damage may be detected from very shortly after a head injury-a fact that may give rise to some challenging diagnostic problems. Early axonal injury detected by means of beta APP immunostaining should be interpreted with caution. The most useful tools currently available for detecting axonal damage are antisera to beta APP, PG-M1, and GFAP, used in conjunction with a routine haematoxylin and eosin stain, but even with immunocytochemistry precise dating of histological changes may not be possible.