The yields of essential oils obtained from dried leaves ofEucalyptus citriodoraandE. camaldulensisranged according to the location between 2.3% and 5.9% forE. citriodoraand between 0.6% and 1.4% forE. camaldulensis.Twenty-eight components were identified by GC/MS. InE. citriodoraandE. camaldulensis, 90% of the isolated oils were obtained after one hour distillation and they contained maximal amounts of citronellal (75%) forE. citriodoraoil and 1,8-cineole (47–71%) forE. camaldulensisoil. At longer isolation times further quantities of oils collected became negligible and the proportions of the main constituents fell significantly. The chemical composition of the oils ofE. citriodoraandE. camaldulensisobtained from plants located in the economically most relevant areas of Benin depended on location and harvesting time. The effects of these two parameters are different for the two oils. An oil ofE. citriodorarich in citronellal (>75%) could be obtained throughout the year with a yield of 5% at Calavi, while even at the best time (June to August) the yield of oil was only 2.5% at Kétou. ForE. camaldulensis, the best yield was approximatively 1.3% at Calavi (February-March) and Kétou (April-May). The Sémé-Ekpé location afforded an oil with a high level of 1,8-cineole (70%) with highest yield in February-March. The Calavi location was exploitable only during that period.