Aim of study is to identify the correlation of CVP and Ive diameter, IVC index, IVC/AO in shock patients. A prospective, cross sectional study was done in 60 shock patients and 60 healthy volunteers, at Emergency department, Cho Ray hospital from 1/1/2013- 31/5/2014. The result showed that the mean IVC in health volunteers was 16.9 mm, IVC index was 32 percent. The correlation of CVP and IVCdiameter was 0.42, CVP and IVC index was 0.32, CVP and IVC/AO was 0.31. If IVC 12.5 mm, estimated CVP 10 Cm H2O with sensitivity was 100 percent, specificity was 76.2 percent. If IVC 15.5 mm, estimated CVP 10 Cm H2O with sensitivity was 100 percent, the specificity was 60 percent.