In order to satisfy the self-sufficiency of plasma, the Korean Red Cross has opened many blood donation offices, where many apheresis machines have been installed for plasmapheresis. It is very important for the donors to feel comfortable on plasmaphersis because they may donate frequently. Plasma hemoglobin can cause problem to both donors and patients. In this study, plasma hemoglobin was compared between pheresis machines (Fenwal Autopheresis C system vs Fenwal Autopheresis C system mini instrument vs Haemonetics Mobile collection system vs Haemonetics Plasma collection system). Plasma hemoglobin in FFP was also measured. Amount (Mean ± SD) of plasma hemoglobin by Auto-C and Mini Auto-C of Fenwal`s was 2.87 mg/dL ± 2.02 mg/dL and 3.86 mg/dl ± 2.77 mg/dL respectively. And that of PCS and MCS was 2.86 mg/dL ± 1.56 mg/dL and 1.94 mg/dL ± 2.58 mg/dL respectively. There was no statistically significant difference between machines of the same companies. However amount of free hemoglobin was lower in plasma collected by Haemonetics (p=0.013) even though amount of free hemoglobin generated by each machines of both companies was with in the normal range of human plasma hemoglobin. Amount of free hemoglobin in FFP was in the middle between that of Fenwal`s and Haemonetics`. High level of free hemoglobin by Fenwal`s is thought to be caused by membrane filter that is installed to prevent red cell contamination from plasma. This results dosen`t mean that red cell itself is more contaminated in Fenwal`s. Considering that amount of free hemoglobin in all the plasma was within the normal range, it can be concluded that all the machines tested in this study can be used doesn`t cause any problem occured by free hemoglobin.