Objective: The purpose of this study was to develop a methodology on computed tomography (CT) perfusion source images for an acute ischemic stroke in predicting infarct core and penumbra. Methods: Computed tomography examinations, including non-contrast enhanced CT, CT perfusion and CT angiography, were performed on 24 patients with symptoms of stroke in less than 9 hours. The Alberta Stroke Program Early CT Score (ASPECTS) was analysed on arterial and venous phase CT perfusion source images and then compared with the ASPECTS on follow-up imaging for an efficacy assessment. Results: The ASPECTS on arterial phase CT perfusion source images was significantly different from venous phase CT perfusion source images (z = -2.812, p = 0.005); linear regression analysis revealed that there was a statistically significant relationship between venous phase CT perfusion source images and the follow-up imaging (beta = 0.715, p = 0.003). Conclusion: The limited data suggested that CT perfusion source images of both arterial and venous phases may have the potential of being used as an assessment for infarct core and penumbra in acute ischemic stroke. [Neurol Res 2009; 31: 351-354]