Objective: To evaluate the clinical application of CT perfusion imaging (CYPI) and CT subtraction angiography (CTSA) in the diagnosis of acute ischemic cerebrovascular disease (AICVD). Methods: 24 cases with AICVD onset within 24 hours were examined with regular CT, CYPI and CTSA. Some of them took CTPI, MRI, MRA, DSA, SPECT by follow-up examinations. Results: In 24 cases 11 had regular CT negative results after onset of stroke 3 ~ 6 hours in 6 cases, 6 ~ 12 hours in 3 cases, 12 ~ 24 hours in 2 cases. Ten cases of them were confirmed by CTPI as having ischemic lesions, 2 cases had middle cerebral artery occlusion (MCAO), and 1 had transient ischemic attack (TIA) with CTPI negative. In 24 cases 13 had regular CT positive rseults, 9 cases had ischemic lesions larger in CTPI than in regular CT, 1 case had MCAO and 1 case had internal carotid artery occlusion(ICAO). There were 4 cases with ischemic lesions on regular CT almost having the same range as that of lacunar infarction in CTPI. The peak value of time(PT), mean transit time(MTT), relative flow (RF) in all 24 cases were found obviously changed. The side of ischemic lesion as compared with the opposite side, and the core of ischemic lesion as compared with peripheral zone were found changed significantly (P < 0.01). Conclusions: Combining use of CTPI and CTSA is indicated for detecting the acute ischemic lesion in early or far more early stage and it is helpful to distinguish TIA, lacunar infarction and larger area of infarction. By semiquantitative analysis on blood prefusion statue, CTPI plus CTSA is possibly to determine the position, area and range of the ischemic lesion and penumbra, and also to analyse the brain blood perfusion statue . It is helpful for early diagnosis of the occlusion of the entire division of ICA or MCA and meaningful for giving prognosis and treatment.