An experiment was conducted under green house conditions to observe the distribution of vesicular-arbuscular mycorrhizal (VAM) hyphae between plants. Special acrylic root boxes with three compartments were constructed. The two outer compartments, into which the trifoliate orange (Poncirus trifoliata Raf.) seedlings and Bahia grass (Paspalum notatum Flugge.) were transplanted, were separated from the center compartment by a barrier made of a nylon screen of 37μm mesh. The inoculation with a VAM fungus, Gigaspora margarita Becker and Hall, was done in the center compartment. The density of hyphae, percentage of infection, and the number of spores were higher in the Bahia grass compartment than those in the compartment with trifoliate orange. A petri dish experiment showed that although the Bahia grass and trifoliate orange root exudates stimulated the hyphal growth of G. margarita, the length of hyphae in the Bahia grass treatment was longer than that of the trifoliate orange. In this experiment it was possible to observe in detail the distribution of hyphae in the rhizosphere of two plants under intercropping system conditions. These hyphae would be related to the interconnection between plants to promote a network system ; the formation and development of this network system is influenced by some root exudates.