OBJECTIVES: 1) To determine what is the utility change for kidney donors from before to 3 months after donation; 2) To determine the minimal important difference (MID) of a decrease (MIDe) in utility for kidney donors. METHODS: We used data from a prospective multicenter observational study, measuring the Health Related Quality of Life (HRQoL) of kidney donors before and three months after transplantation. Utility scores were estimated using the SF-6D and EQ5D. Two methods were used to estimate the MIDe: i) the anchor-based method by the Global Rating of Change (GRoC) for donors rating their global health “somewhat worse” 3 months after donation;  ii) the distribution-based method by the standard error of measurement (SEM). RESULTS: In total, 211 donors for the EQ-5D and 192 for the SF-6D completed the questionnaire. Results showed a significant (p<.0001) decrease in utility score at three months. The mean (SD) utility score before transplantation was 0.932 (±0.091) with the EQ5D, and 0.834 (±0.085) using the SF-6D, and 0.882 (±0.151) and 0.757 (±0.118) respectively at three months with a significant decrease (<.0001). Half of donors (53.9%)  rated their global health “about the same” and 35 (15.4%) “somewhat worse” at follow up. Using the GRoC method, the MIDe was -0.113 units for the EQ-5D and -0.128 units for the SF-6D. By the SEM method, MIDe was -0.076 for the EQ5D and -0.073 for the SF6D. More than third of patient rechead the MIDe using the SEM method. CONCLUSIONS: This study showed a significant descrease in utility score three months after donation in most donors while reporting their global health “about the same”. The MIDe can be used by clinician as a threshold to identify donors with a meaningful decrease in utility score in a short run after donation.