GP73 is a transmembrane glycoprotein that increases in viral and non-viral liver diseases, especially in hepatocellular carcinoma. This study aims to evaluate the effect of sample type and storage conditions on GP73 concentration. Twenty subjects were enrolled in this study. Serum and citrated plasma samples were collected. Both were subjected to different time intervals and storage temperature. Baseline GP73 concentrations ranged from 1.7 to 16.9 ng/mL in serum samples, and from 1.1 to 15.3 ng/mL in citrated plasma (Mann–Whitney U test, p¼.1). The acceptable change limit for GP73 was 6.1%. As the highest value of the median percentage deviation was 5.3% in both sample types at different storage condition so, deviations were within the accepted limits. But there were considerable variations in the GP-73 concentrations after 2 cycles of freezing and thawing at 20 C. This study shows that both serum and citrated plasma can be used for the measurement of GP73 concentration. GP73 seems to be stable under common storage conditions, but it may be unstable with frequent cycles of freezing and thawing.