abstract the peel oil compositions of four kinds of sweet oranges in china, citrus sinensis osbeck var. hongjian, c. sinensis osbeck var. anliu, c. sinensis osbeck var. sihui and c. sinensis osbeck var. washington navel, were investigated by gc and gc/ms. the essential oils were extracted by cold-pressing method. forty-two to 53 compounds were quantitatively determined for each variety. their percentages, respectively, were: > 97.3%, > 98.4%, > 97.5% and > 98.0% in hydrocarbons; > 1.5%, > 0.7%, > 0.8% and > 0.9% in total aldehydes; 0.8%, 0.5%, 0.5% and 0.5% in alcohols. either cis-or trans-limonene oxide was detected in small amounts in each of the four samples, with hongjiang containing both limonene oxides. -3-carene was commonly quantified at a level of 0.1% in all the samples. the content of aliphatic aldehydes, including octanal, nonanal, decanal and dodecanal, exceeded that of terpene aldehydes, such as neral and geranial in hongjiang (0.9%) and washington navel (0.6%), whereas the aliphatic aldehydes in anliu and sihui were present to a lesser degree than the terpene aldehydes. either - or -sinensal was detected in trace amounts in each of the four samples. linalool was the major alcohol in all the samples. nootkatone was not detected.