A simple, quantitative method was developed to determine peanut (Arachis hypogaea L.) maturity. The method is based on the changing seed-hull weight ratio during maturation of the fruit. The ratio or maturity index was determined for fresh as well as air-dried pods, and these ratios correlated well with a physiological maturity index. The relationship between arginine maturity index and the air-dried seed-hull maturity index (DMI) was also determined, and the two indexes were negatively correlated. The DMI values across nine planting and eight harvest dates over a 2-year period showed that DMI could be applied to estimate average peanut seed maturity under field harvest conditions. The two peanut varieties tested, Florigiant and Florunner, were found to differ in maxmum DMI values. The study also showed that peanut seed weight increased with maturity then decreased after full maturity.