We studied antagonism among fungal endophytic species, based on within-leaf distribution and dual cultures of fungal dominants in Quercus myrsinifolia and Eurya japonica, major components of natural forests in Kanto area and also used as a wind-break forests and hedges. The leaf samples were taken from secondary forests in Kashiwa, Chiba and from co-occurring trees in a Japanese cedar and Hinoki cypress plantation in Mt. Wagakuni, Ibaraki in September 2008 and October 2008, respectively. Endophytic fungi were isolated from 2 mm×2 mm segments taken from five different portions of each surface-sterilized leaf : petiole (P), basal part of the midrib (Bm), basal part of the lamina without vein (Bl), distal midrib (Dm), distal lamina (Dl). The segments were incubated on 1/2 PDA plates. In Q. myrsinifolia leaves, two dominant fungi appeared different within-leaf position and tissue, namely, Phomopsis sp. was frequently isolated from P and Bm of leaves from Q. myrsinifolia in both sites and E. japonica in Kashiwa, while Tubakia sp.1 dominated in Bl and Dl of Q. myrsinifolia leaves in Kashiwa. The result that dual cultures of these two species displayed inhibition of colony growth suggested their potential antagonism. These results suggested that fungal distribution within a leaf is influenced by interactions between fungal species through habitat segregation.