Hemorrhagic transformation of an ischemic stroke can occur as stroke progresses or as a complication of stroke treatment. Hemorrhagic transformation varies in severity and is divided into four subtypes. Small petechial bleedings along the margins of the infarct constitute hemorrhagic infarction (HI) type 1, with more confluent petechial bleeding constituting HI type 2. Parenchymal hematomas (PH) are frank hematomas that are categorized in hemorrhages that consist of less than 30% of the infarct area without substantial mass effect (PH type 1) or consist of more than 30% of the infarct area with a space occupying effect (PH type 2). Some large hematomas result in acute neurological deterioration with high mortality rates; these hemorrhages causing acute neurological deterioration are classified as symptomatic intracranial hemorrhage (sICH). In most of these cases PH2 is the underlying hemorrhagic transformation subtype. Smaller hemorrhages have no or less apparent clinical consequences than large hemorrhages and their precise impact on outcome remains unclear. Additionally, it is unclear which patients are at increased risk for hemorrhagic transformation and whether that risk is modifiable. In this thesis, we showed that hemorrhagic transformation is associated with a poor functional outcomes. Several markers of large final infarcts such as poor collateral score and high NIHSS were associated with HI while clinical markers such as blood pressure and atrial fibrillation were associated with PH and sICH. Hemorrhagic transformation classified on NCCT and B0 EPI are not readily comparable. Last, patients treated within 4.5 hours after stroke onset do not have an increased risk for hemorrhagic transformation after treatment with IVT compared with EVT without IVT. Patients without successful reperfusion and IVT were more prone to developing subarachnoid hemorrhage.