INTRODUCTION: Recent availability of lyophilized fresh frozen plasma(Lyo-FFP) and lyophilized platelet(Lyo-PLT) on thromboelastography(TEG) may help to target therapy with the required blood product and thereby correct coagulopathy. This study was performed to assess the in vitro effect of LyoFFP and Lyo-PLT on human blood diluted with normal saline by TEG. METHODS: Venous blood from 8 healthy volunteers was diluted to 50volume%(D1) and 75volume%(D2) with 37degreesC normal saline for native TEG. Then, D1 and D2 were mixed with 0.5 ml citrate for citrate TEG(CD1 and CD2). The TEGs of CD1 and CD2 treated with Lyo-FFP and Lyo-PLT were compared with TEGs of D1, D2, CD1 and CD2 . All of blood samples were checked for hematocrit, platelet count and fibrinogen concentration. All the TEGs were compared for significance of differences by repeated measure ANOVA. RESULTS: D1 and D2 showed much lower hematocrit, platelet count and fibrinogen than control. In serial hemodilution there were significant changes in only maximal amplitude(MA) in D1 and all TEG parameters in D2 were depressed. Addition of Lyo-FFP and Lyo-PLT to D1 did not show any positive change in TEG parameters. However, addition of Lyo-FFP and Lyo-PLT to D2 showed significant improvements in reaction time and alpha angle, but not in MA. CONCLUSIONS: Lyo-FFP may be helpful in determining therapy for bleeding associated with coagulation factor deficiencies. However, the role of Lyo-PLT for the detection of platelet deficiency needs further evaluation.