The right lobe liver graft has become the workhorse of adult-to-adult live donor liver transplantation. Donor right hepatectomy is feasible only because of the immense regenerative ability of the liver. The long-term biological consequences of this very major donor procedure on the donor however are unknown. Twenty-nine donors of this procedure in our centre, all of whom included the middle hepatic vein, were studied. On long-term follow-up at a median of 47.4 months, there was a discernible but statistically insignificant decrease in size of the regenerated left lobe compared to the original whole liver volume. There was paradoxically a trend of incompleteness of regeneration in relation to the original liver volume for those with a larger remnant left lobe. The volume ratio of the regenerated left lobe to the original left lobe before hepatectomy was inversely proportional to the left lobe proportion preoperatively. This strong but inverse linear correlation reflected the good regenerative ability of the remnant left lobe. None of the donors developed thrombocytopenia. Although demonstrable decrease in white cell count, increase in serum alanine aminotransferase, aspartate aminotransferase, and creatinine did occur, the changes remained within normal limits and were of yet uncertain clinical significance. In conclusion, donor right hepatectomy including the middle hepatic vein is biologically acceptable to the live donor. Liver Transpl 12:259–263, 2006. © 2006 AASLD.