In this study there were 558,089 donor samples, of which there were 1664 donor samples found to be HBsAg reactive. All of the 1664 samples were tested for anti-HBc and HBsAg and confirmed by neutralisation, and those that were HBsAg positive and anti-HBc positive totaled 484, while those that were HBsAg positive and anti-HBc negative totaled 94; those that were HBsAg negative and anti-HBc positive totaled 326, and those that were HBsAg negative and anti-HBc negative totaled 760. 746 of the 1664 were repeat donors, the mean of interdonation interval for repeat donors was about 11.9 months, and the interdonation interval data for all 746 repeat donors is shown in Table 4 . Table 4The interdonation interval data for all 746 repeat donorsThe interdonation interval (month)6-9(including 9)9-1212-1515-1818-2121-24>24 TotalDonors3391946234415719,746Mean(month)11.9