Inadequate levels of calcium in the soil can lead to peanut seed abortion and poor germination of harvested seed. Since little root-absorbed calcium is translocated to the developing underground fruit, the peanut pod must absorb calcium directly from the soil. However, the exact timing and role of calcium in normal peanut fruit development remain largely unknown. The effect of calcium levels on the timing and extent of seed development and germination is being examined in both controlled growth chamber and field experiments. A study in which the fruiting medium was separated from the rooting medium allowed controlled addition of calcium to the underground pegs and developing fruit, under defined temperature and light conditions. Pegs were removed from the fruiting medium at time points during early development for observation. To further investigate the response of young, underground developing fruit to soil calcium levels, a replicated field study was conducted using two runner peanut cultivars, Georgia Green and the larger-seeded C-99R, grown at low and high calcium levels. Developing fruit was harvested monthly from 60 days after planting and scored for developmental stage and evidence of seed abortion. To determine the role of calcium in the poor seed germination of peanut varieties, such as the late maturing, disease resistant cultivar DP-1, four runner peanut cultivars, AP-3, C-99R, DP-1 and Georgia Green, were grown at four rates of calcium (none, 700, 1400, and 2100 pounds gypsum per acre). Increased soil calcium resulted in increased soil germination of C-99R, but not the other genotypes, suggesting that calcium was not responsible for the poor germination of DP-1. Greater understanding of the role of calcium in early fruit development may facilitate strategies to improve yield and quality of peanuts.