abstract the chemical variation of volatile constituents from leaves of pimenta pseudocaryophyllus collected bimonthly for one year from a locality in the atlantic rain forest, southeastern brazil, was determined by gc/ms. seven com- pounds were identified and characterized, revealing a predominance of phenylpropanoids (15.4-70.9%) and variable amounts of monoterpenes (0.5-5.3%). the composition of the oil changed month by month. the best yield of oil was obtained in november, and the major component chavibetol was present in all samples (50.2-70.9%). the chavibetol content showed significant seasonal variation, with the maximum percentages of 69.1% and 70.9% measured in january and november, respectively key word index: seasonal variation pimenta pseudocaryophyllus chavibetolessential oil