The leaf essential oil of Casimiroa edulis (Rutaceae), collected from Monteverde, Costa Rica, has been obtained by hydrodistillation and analyzed by GC-MS. The leaf oil was dominated by sesquiterpene hydrocarbons, predominately germacrene D (16-22%) and (E)-caryophyllene (16-17%), consistent with the traditional use of this plant as a sedative, sleep inducer and hypotensive.