The chemical composition of the peel and leaf oils of four MalaysianCitrus species (C. hystrixD.C.,C. aurantifoliaSwingle,C. maximaMerr. andC. microcarpaBunge) was examined by co-chromatography, two columns of different polarity, GC/MS and linear retention indices. β-Pinene and limonene were the major constituents of the peel oils ofC. hystrix(39.3% and 14.2%) andC. aurantifolia(28.4% and 39.3%). The peel oils ofC. maximaandC. microcarpawere found to be rich in limonene (>94%). Citronellal at 72.4% was the most abundant compound in the leaf oil ofC. hystrix.The major components of the leaf oil ofC. aurantifoliawere geranial (19.4%), limonene (16.4%) and neral (11.4%). Sesquiterpenes were present at 70.8% in the leaf oil ofC. microcarpawhere hedycaryol (19.0%), β-sesquiphellandrene (18.3%) and α-eudesmol (14.4%) were the major constituents. The leaf oil ofC. maximacontained significant amounts of phytol (23.1%) and β-caryophyllene (15.4%).