Seed moisture at harvest is a key variable affecting seed performance following conditioning.  Accurate seed moisture readings are necessary for determining optimal harvest timing and drying rate.  This poster addresses biological variation in maize seed moisture ear-to-ear and within ear. Nine detasseled inbreds representing a range of relative maturities were pollinated with a mixed male pollinator.  Five ears of each inbred were sampled at 43%, 35% and 27% moisture.  Each ear was divided into four equal parts from butt to tip and seed was oven dried.  Depending on the inbred, ear-to-ear moisture variation ranged from 2-9 percentage points at 43% moisture harvest, 4-11 percentage points at 35% moisture harvest and 2-13 percentage points at 27% moisture harvest. Tip to butt moisture variation was as high as 11% for some inbred ears. Implications for seed production:  random ear sampling, complete shelling and uniform mixing should provide a good composite for moisture measurement that represents the field.  However, inherent biological variation in seed moisture will result in moistures + / -  5% from the average moisture reading. Practices that reduce biological variation within the field may contribute to seed quality and performance.