Rationale: Recently our study group reported the results of the Basilar Artery International Cooperation Study (BASICS), a prospective registry of patients with an acute symptomatic basilar artery occlusion (BAO). Our observations in the BASICS registry underscore that we continue to lack a proven treatment modality for patients with an acute BAO and that current clinical practice varies widely. Furthermore, the often-held assumption that intra-arterial thrombolysis (IAT) is superior to intravenous thrombolysis (IVT) in patients with an acute symptomatic BAO is challenged by our data. The BASICS registry was observational and has all the limitations of a non-randomised study. Interpretation of results is hampered by the lack of a standard treatment protocol for all patients who entered the study.