We present a 39-year-old woman with transient global amnesia (TGA) who showed sudden onset amnesia immediately following sexual intercourse after taking a bath. Her amnesia resolved within 6 hours. Three-Tesla (3T) diffusion weighted magnetic resonance imaging (DWI) taken 80 hours after the onset revealed hyperintense spots in the CA1 subfields of the bilateral hippocampi. No abnormalities were noted in 3T DWI, T(2) weighted imaging (T(2) WI) and fluid attenuated inversion recovery (FLAIR) at 3 weeks after the onset. She had no cardiovascular diseases. Magnetic resonance venography (MRV) revealed hypoplasia of the right transverse sinus and stenosis of the bilateral brachiocephalic veins. Ultrasound sonographic studies revealed a prolonged retrograde flow component of the right internal jugular vein during a Valsalva maneuver. The vast majority of TGA attacks occur between the ages of 50 and 80, and very rarely under the age of 40 years, which is mostly not exposed to vascular risks. We therefore speculate that in conjunction with a decreased vascular beds from the brain, a Valsalva-like maneuver might have precipitated cerebral venous ischemia in the bilateral hippocampi, which are the most vulnerable to ischemic insults.