A steam distilled oil obtained from the leaves of Piper barbatum H.B.K.;grown in Peru, in the Amazon basin, was analyzed by capillary GC and GC/MS. Fifty-three components amounting to 98.3% of the oil were characterized from which 17 (totalling 86.6%) were found to be arylpropanoids. The oil contained 2-methoxy-4,5-methylenedioxypropiophenone (29.5%), Î±-asarone (14.1%), apiole (8.9%), Î²-asarone (9.4%), methoxy-4,5-methylenedioxypropiophenone isomer (10.9%), and (Z)-isoelemicin (9.5%) as major constituents of the oil.