This study sought to determine whether a prognostic score is a useful indicator of donor safety using 13 consecutive donors enrolled for liver transplantation. The donor operations were right hepatic lobectomies (n = 10) and left hepatic lobectomies (n = 3). The postoperative maximal level of serum total bilirubin was used to assess the magnitude of surgical stress. Variables such as donor age, percentage of liver resection (PLR), indocyanine green 15-minute retention rate (ICGR15), operative blood loss, operation time, prognostic score and graft weight were evaluated as predictors of the magnitude of surgical stress. The PLR and prognostic score (PS) were calculated according to the following formulae: PLR (%) = 100*Graft weight (g)/standard liver volume of the donor (mL); PS = -84.6 + 0.933*PLR (%) +1.11*ICGR15 (%) +0.999*age (years); Standard liver volume (mL) = 706.2*body surface area (m2) + 2.39. No serious complications occurred after the donor operations. Maximal bilirubin ranged from 1.9 to 10.9 mg/dL. There were no mortalities, although there were two morbidities, bile leakage and prolonged liver dysfunction. Postoperative hyperbilirubinemia was observed in two donors and in one Gilbert's syndrome donor. Linear regression analysis of each variable indicated poor correlations between those variables and maximal bilirubin. However, close correlations were seen between maximal bilirubin and both donor age and PS except for the three patients who showed postoperative hyperbilirubinemia. In these uneventful donors, statistical formulae were obtained as follows: maximal bilirubin (PMB) = 0.271 + 0.056*donor age (correlation coefficient 0.612, P < .008), PMB = 1.541 + 0.059*PS (correlation coefficient 0.597, P < .009). In conclusion, PS is useful to predict maximal bilirubin and to ensure donor safety.