Abstract The composition of the essential oil from leaves of Zanthoxylum procerum Donn. Sm. from Costa Rica, was analyzed by capillary GC/FID and GC/MS. Seventy-eight compounds were identified corresponding to ca. 97% of the oil. The major components were the monoterpenoids β-phellandrene (30.0%), α-pinene (8.5%), myrcene (7.1%), α-phellandrene (6.1%), limonene (4.9%), and linalool (4.5%) and the sesquiterpenes germacrene D (8.1%) and β-caryophyllene (7.0%). Key Word Index: Zanthoxylum procerum Rutaceaeessential oil compositionβ-phellandrene