Recently new criteria for diagnosing vascular dementia (VaD) have been suggested by (a) the State of California Alzheimer's Disease Diagnostic and Treatment Centres (ADDTC) and (b) the NINDS-AIREN group after an international workshop convened by the National Institute for Neurological Disorders and Stroke (NINDS), with support from the Association Internationale pour la Recherche et l'Enseignement en Neurosciences (AIREN). We have retrospectively applied the new criteria to two groups of patients who are thought by us to be suffering from VaD. The first group (20 patients) had a raised Hachinski Ischaemic Score, i.e. 7 or more (mean HIS = 9.5), and a second group (20 patients) with an HIS between 4 and 6 points (mean HIS = 4.9). In group 1, 19 patients fulfilled the ADDTC criteria for probable or possible VaD, compared with 16 patients who fulfilled the NINDS-AIREN criteria. In group 2, 11 patients fulfilled the ADDTC criteria for probable or possible VaD, compared with only five patients who fulfilled the NINDS-AIREN criteria. This suggests that the ADDTC criteria may be more sensitive than the NINDS-AIREN criteria and the HIS. However, post-mortem validation studies of the new criteria are needed to determine if the improved sensitivity of the ADDTC criteria is at the expense of their specificity.