Kernels at the upper position of a maize ear usually show poorer filling and lower weight in contrast to those at the basal position. The mechanism has not been understood. The experiments were conducted using a maize cultivar Denghai 11, grown in both field and greenhouse conditions, to determine number of endosperm cells, kernel filling rate, and contents of zeatin (Z) + zeatin riboside (ZR), indole-3-acetic acid (IAA), abscisic acid (ABA), and gibberellin-3 (GA3) in the kernels at different positions on an ear from silking to maturity. The results indicated that the maximum number of endosperm cells, maximum division rate of endosperm cells,