Considerable interest has been shown in the potential anti-inflammatory effects of polyunsaturated fatty acids (PUFAs) in multiple sclerosis (MS) and other autoimmune inflammatory disorders. Studies suggest a modest association between consumption of low levels of unsaturated fat and an increased incidence of MS. Moreover, in vitro and in vivo studies have demonstrated that omega-3 and omega-6 PUFA supplementation can reduce immune-cell activation via a number of complex pathways. Noncontrolled and controlled clinical trials of PUFA supplementation in patients with MS have, however, provided mixed results. These studies had important limitations in design and selection of outcome measures, and these factors might partially explain the inconsistent results. We propose that the potential role of PUFAs as disease-modifying, anti-inflammatory treatments for MS should be revisited in proof-of-concept trials that use accepted MRI outcome measures.