['To quantify the risk for bleeding complications after thrombolysis for ischemic stroke in patients on warfarin (international normalized ratio [INR] ≤ 1.7) and to put these data into perspective with previous studies.', 'A total of 548 consecutive stroke patients receiving IV recombinant tissue plasminogen activator (rtPA) were prospectively evaluated and details about warfarin pretreatment were carefully recorded. Prothrombin time-based INR values were measured before thrombolysis and 6 and 24 hours thereafter. Intracranial hemorrhage occurring within 72 hours was assessed by CT examinations and defined according to National Institute of Neurological Disorders and Stroke criteria. Main outcome variables were symptomatic intracranial and major systemic bleedings.', 'Of the 548 patients, 33 (6.0%) and 14 (2.6%) experienced symptomatic intracranial and major systemic bleedings, respectively. Patients taking warfarin until the day of or day before admission (n = 15, mean ± SD INR 1.21 ± 0.32 vs 1.01 ± 1.12, p = 0.030) faced an approximately 4-fold risk for intracranial hemorrhage (20.0% vs 5.6%, unadjusted odds ratio [OR] [95% confidence interval (CI)] 4.2 [1.1-15.7], p = 0.033). Findings were similar after adjustment for age, NIH Stroke Scale score, and diabetes (adjusted OR [95% CI] 4.1 [1.0-16.1], p = 0.044) and when focusing on any major bleeding (intracranial or systemic) (unadjusted OR [95% CI] 4.1 [1.3-13.6], p = 0.019). Half of the patients with bleedings showed an INR rise above 1.7 6 hours after thrombolysis. A meta-analysis yielded confirmatory yet heterogeneous results (unadjusted OR [95% CI] derived from a random effects model, 2.31 [1.15-4.62], p = 0.018, I(2) = 58% [11%-80%]).'] Does subtherapeutic warfarin therapy entail an increased bleeding risk after stroke thrombolysis?