Susac's syndrome is considered a rare differential diagnosis in the work-up of suspected multiple sclerosis. Over the last decade or so, significant advances in our understanding of Susac's syndrome mean that it can now be readily distinguished from multiple sclerosis in the majority of cases with a careful history and close attention to MR imaging. Supporting investigations such as CSF examination, fluorescein angiogram, visual field perimetry and audiology often yield important clues. In milder cases, however, diagnostic uncertainty can exist, and forme frustes of the disease are recognised. In this article, we discuss the clinical features of Susac's syndrome with emphasis on the findings and investigations that help to differentiate it from MS.