Objective: To review cases of 9DWI negative9 stroke admitted to the Fremantle Hospital Stroke Unit; to examine which stroke syndromes are most commonly DWI negative and to postulate reasons for this. Background MRI is increasingly being used as the diagnostic tool of choice for acute ischaemic stroke. It is more sensitive than CT in this regard, with an accuracy approaching 95%. It is recognised that a proportion of clinically diagnosed strokes show no DWI changes on MRI, and we have identified certain stroke syndromes that are more commonly DWI negative. Design/Methods: The Fremantle Hospital stroke database was used to retrospectively review all admissions for acute ischaemic stroke to the Stroke Unit between November 2005 and June 2011. All diagnoses were made by experienced Stroke Neurologists. All MRI scans were reviewed by blinded neuroradiologists. Results: 996 patients were admitted to the Stroke Unit with the diagnosis of acute ischaemic stroke. 701 patients had an MRI as part of their management and 20 patients had no DWI changes on MRI. 7 were female and 13 male. The median age of this population was 71. Median time from symptom onset to MRI was one day. The most common DWI negative stroke syndromes were ataxic hemiparesis and internuclear opthalmoplegia. 19 of the 20 cases were either posterior circulation or lacunar strokes. Conclusions: Certain phenotypes of stroke are more commonly associated with negative MRI, notably posterior circulation and lacunar strokes. Hypotheses regarding this will be discussed in detail. Whilst MRI has revolutionized the assessment of acute ischaemic stroke, we have identified certain clinical syndromes where MRI may be less reliable. These results should serve to remind physicians to continue to use clinical judgment in the diagnosis of ischaemic stroke. Disclosure: Dr. Watts has nothing to disclose. Dr. Alvaro has nothing to disclose. Dr. Kelly has nothing to disclose. Dr. Wood has nothing to disclose.