Three specimens of Ayapana triplinervis (Vahl) R.M.King & H. Rob from Reunion Island (Indian Ocean) collected at two distant locations (North of the island; samples 1 and 2, South of the island; sample 3), in different growth phases (flowering; samples 1 and 3, vegetative; sample 2) were investigated for their leaf essential oil compn. This study reports the chem. character of this species on the island and investigates the relationship between essential oil compn., developmental stage and geog. location. Anal. by GC-FID and GC-MS enabled us to identify and quantify a total of 39 constituents accounting for 97.1-98.0% of the oils. The three essential oil samples, all obtained by hydrodistn., showed a high percentage of the arom. compd. thymohydroquinone di-Me ether (89.9-92.8%). All other minor components remained more or less unchanged both qual. and quant. with respect to the stage of growth. On the contrary, variations were obsd. with geog. distribution. The geog. variation of the chem. compn. of the volatile oil of A. triplinervis from several sites in the world is also briefly discussed.