Preliminary screening test of modulators for multidrug resistance with 400 medicinal plants was carried out by using human multidrug resistance cell line, KB-V1. Among active medicinal plants, the unripe fruits of Evodia officinalis showed a potent modulating activity of MDR. From MeOH extract of this plant, we isolated two indole alkaloids, rutaecarpine (1) and evodiamine (2), by repeated silicagel column chromatography. Rutaecarpine increased the cytotoxicities of vinblastine and taxol against multidrug resistance cells, but evodiamine showed no modulating activity in spite of its potent cytotoxic activities.