The study was carried out to find out the differences in composition of oils obtained from healthy, naturally infected and artificially screws wounds eaglewood (Aquilaria agallocha Roxb.) using gas chromatography mass spectrometry analysis. Natural healthy plants agar contained octacosane (19.83%), naphthalene, 1,2,3,5,6,7,8,8a-octahydro-1,8a-dimethyl-7-(1-methylethenyl)-, [1R- (1.alpha.,7.beta.,8a.alpha.)]-(12.67%), 5-isobutyramido-2-methyl pyrimidine (13.52%), caryophyllene oxide (11.25%) and (.+-.)-cadinene (5.46%). Natural infected plants agar (super agar) contained cycloheptane, 4-methylene-1-methyl -2-(2-methyl-1-propen-1-yl)-1-vinyl- (46.17%), caryophyllene oxide (33.00%) and 7-isopropenyl-4a-methyl-1-methylenedecahydronaphthalene (20.83%). Artificially screw injected plants agar contained diisooctyl phthalate (71.97%), 1H-cycloprop[e]azulen-4-ol, decahydro-1,1,4,7-tetramethyl-, [1ar- (1a.alpha.,4.beta.,4a.beta., 7.alpha., 7a.beta., 7b.alpha.)]-(9.16%), hexadecanoic acid (7.05%), naphthalene, 1,2,3,5,6,7,8,8a-octahydro-1,8a-dimethyl-7-(1- methylethenyl)-, [1R-(1.alpha.,7.beta.,8a.alpha.)]-(6.45%) and aristolene (5.36%). This study showed a marked difference in the oil compositions among the treatments with regards to their quality.