Objective To investigate the influence on right-to-left shunt (RLS) of patent foramen ovale with contrast transcranial Dopple (cTCD) in different positions.Methods 276 consecutive patients included ischemic cerebrovascular disease (ICVD),migraine,episodic vertigo and syncope.They underwent cTCD at rest and after Valsalva maneuver in 4 positions:upright sitting,supine,left lateral decubitus and right lateral decubitus,in random order.RLS was graded 0 (no microbubbles detected),1 (1-10microbubbles),2 (＞ 10 microbubbles but no curtain),and 3 (curtain,shower of microbubbles).Meanwhile,each patients was examined by contrast transthoracic echocardiography(cTTE),contrast transesophageal echocardiography (cTEE) or right heart catheterization.Results RLS detection rate was 48.2％ (133/276)through cTCD.They were also confirmed patent foramen ovale by 82 cases in cTTE,28 cases in cTEE,and 23 patients in right heart catheterization.At rest,RLS detection rate and microbubbles of 4 positions had no significant difference (P ＞0.05).After the Valsalva maneuver,RLS detection rate and microbubbles of each position were significantly higher than at rest (P ＜0.001),and the RLS detection rate and microbubbles in upright sitting were higher than that at rest(P ＜0.05).Conclusions RLS is best detected in the upright sitting position with Valsalva maneuver with cTCD.Upright sitting detection helps to improve the detection rate and microbubbles of RLS.