The essential oils of eight samples of Piper aduncum L., collected at different localities of the Amazon region, were analysed by GCâMS. The major component identified in all samples was dillapiole (31.5â97.3%). Sample A, collected at Serra do Navio (AP), showed a yield of oil and dillapiole content of 3.3% and 31.5%, respectively; sample B, collected at Melgaço (PA), 1.8% and 50.8%; sample C, collected at Benfica (PA), 1.6% and 56.3%; samples D and E, collected at Belém (PA), 1.2% and 82.2%; 1.5% and 86.9%, respectively; sample F, collected at Manaus (AM), 3.4% and 91.1%; sample G, collected at Road Manaus-Caracaraí, km 30 (AM), 3.0% and 97.3%; sample H, collected at Cruzeiro do Sul (AC), 3.2% and 88.1%. The yield of oil and dillapiole content of samples of P. aduncum occurring in Malaysia and Fiji showed 1.3% and 64.5%; and 0.5% and 58.0%, respectively. By comparison, the plants growing wild in Amazonas State had the highest oil yield and dillapiole content. © 1998 John Wiley & Sons, Ltd.