Technical Abstract: Drought at pod filling and maturity stages can severely reduce yield of peanut. Better root systems can reduce yield loss from drought. The goal of this study was to investigate the responses to terminal drought of peanut genotypes for root dry weight and root length density. A field experiment was conducted at Khon Kaen University’s Agronomy Farm in 2010/2011. A split plot design with four replications was used in this study. Five peanut genotypes; ICGV 98308, ICGV 98324, ICGV 98348, Tainan 9 and Tifton 8 were assigned as main plots and two soil moisture levels [field capacity (FC) and 1/3 available water (1/3 AW) at R7 growth stage through harvest] were assigned as subplots. Data were recorded for relative water content (RWC), root dry weight (RDW) and root length density (RLD) at the last day of irrigation, R7 stage and harvest. Pod yield (PY), biomass (BM) and harvest index (HI) were recorded at harvest. Drought significantly reduced pod yield, biomass and harvest index, and differences among peanut genotypes for these traits were observed. ICGV98324 was the best genotype for pod yield and harvest index under drought, whereas Tifton 8 was the best genotype for biomass. ICGV98348 gave the highest drought tolerance index (DTI) for pod yield, biomass and harvest index. Drought did not significantly affect root dry weight, but peanut genotypes were significantly different for this trait. Tifton 8 had the highest root dry weight. Differences among peanut genotypes were also observed for root length density. A higher root length density at deeper layers may allow plants to mine more available water in the sub-soil. Genotypes showed differential responses for root growth and distribution. Gentoypes with higher pod yields under stress versus non-stress conditions had more root length density in the deeper soil layers during terminal drought stress compared to the non-stress treatment.