We performed a retrospective study of symptomatic peripheral vascular malformations to determine if MR imaging can be used to distinguish slow-flow venous malformations from high-flow arteriovenous malformations and arteriovenous fistulas. Twenty-seven MR examinations in 25 patients with malformations outside the CNS were reviewed. Sixteen venous malformations, nine arteriovenous malformations, and two arteriovenous fistulas were included. In all cases, the MR findings were correlated with the results of angiography. The distinction between slow-flow venous malformations and high-flow arteriovenous malformations and arteriovenous fistulas was made primarily on T2-weighted MR images, which showed high signal intensity in venous malformations and flow voids in high-flow lesions. In addition to the previously described MR features of venous malformations (serpentine pattern with septations, associated muscle atrophy, and typical T1 and T2 signal intensities), several new MR features were apparent. Venous malformations had a propensity for multifocal involvement (37%), orientation along the long axis of extremities or affected muscles (78%), and adherence to neurovascular distributions (64%). Prominent subcutaneous fat was commonly seen adjacent to the malformation. MR images of arteriovenous malformations and arteriovenous fistulas also commonly showed muscle atrophy and subcutaneous fatty prominence. Our results show that slow-flow venous malformations can be distinguished from high-flow arteriovenous malformations and fistulas on the basis of spin-echo MR signal characteristics. The associated imaging characteristics help in the differential diagnosis in problematic cases.