BACKGROUND AND PURPOSE: The contrast volume transfer coefficient (Ktrans), which reflects blood-brain barrier permeability, is influenced by circulation and measurement conditions. We hypothesized that focal low BBB permeability values can predict the spatial distribution of hemorrhagic transformation and global high BBB permeability values can predict the likelihood of hemorrhagic transformation. MATERIALS AND METHODS: We retrospectively enrolled 106 patients with hemispheric stroke who received intra-arterial thrombolytic treatment. Ktrans maps were obtained with first-pass perfusion CT data. The Ktrans values at the region level, obtained with the Alberta Stroke Program Early CT Score system, were compared to determine the differences between the hemorrhagic transformation and nonhemorrhagic transformation regions. The Ktrans values of the whole ischemic region based on baseline perfusion CT were obtained as a variable to hemorrhagic transformation possibility at the global level. RESULTS: Forty-eight (45.3%) patients had hemorrhagic transformation, and 21 (19.8%) had symptomatic intracranial hemorrhage. At the region level, there were 82 ROIs with hemorrhagic transformation and parenchymal hemorrhage with a mean Ktrans, 0.5 ± 0.5/min, which was significantly lower than that in the nonhemorrhagic transformation regions (P < .01). The mean Ktrans value of 615 nonhemorrhagic transformation ROIs was 0.7 ± 0.6/min. At the global level, there was a significant difference (P = .01) between the mean Ktrans values of patients with symptomatic intracranial hemorrhage (1.3±0.9) and those without symptomatic intracranial hemorrhage (0.8±0.4). Only a high Ktrans value at the global level could predict the occurrence of symptomatic intracranial hemorrhage (P < .01; OR = 5.04; 95% CI, 2.01-12.65). CONCLUSIONS: Global high Ktrans values can predict the likelihood of hemorrhagic transformation or symptomatic intracranial hemorrhage at the patient level, whereas focal low Ktrans values can predict the spatial distributions of hemorrhagic transformation at the region level.