Background and Purpose-There is controversy about the optimal patient position for the detection of right-to-left shunt (RLS). The study was performed to investigate which patient position best detects RLS during contrast-enhanced transcranial Doppler. Methods-We prospectively evaluated consecutive patients with ischemic stroke or TIA referred to our Noninvasive Cerebrovascular Laboratory for suspected paradoxical embolism. The standard protocol for RLS detection recommended by the International Consensus Criteria was followed. Each patient was examined at rest and after Valsalva maneuver in 4 positions: supine, right lateral decubitus, right lateral leaning, and upright sitting, in random order. RLS was graded 0 (no microbubbles [mB] detected), 1 (1-10 mB), 2 (Ͼ10 mB but no curtain), and 3 (curtain, shower of mB). Blood pressure, heart rate, and neurological symptoms were monitored. Data were analyzed using SPSS version 17. Results-RLS