Introduction: A high prevalence of atrial septal defects is reported in patients with cryptogenic ischemic stroke, also related to an increase of the risk of recurrence. Objective: To report case of a young patient with a history of diabetes mellitus and ischemic stroke without arterial changes proven. A transcraneal Doppler study with a bubble test helped to diagnose a patent foramen ovale. Conclusion: As part of the initial evaluation of this patient, a TCD study has helped to clarify the stroke etiology. The demonstration of a patent foramen ovale has implications fo r the secondary prevention of stroke.