The composition of the volatile fraction of Italian sweet orange oil obtained from blond and blood pulp fruits has been studied by GC and GC/MS. The study has been carried out on 190 genuine oils obtained by “Pelatrice” and “FMC in-line” industrial processing during the 1991–92 season. More than 55 components have been identified in the oil, with limonene (ca. 95%) as the main component. Because of the relatively high percentage of octanal and decanal found in the oil, the carbonyl compounds are the most important components of the oxygenated fraction. The results obtained establish that the quantitative composition of sweet orange oil shows peculiar variations in many components during the season and greatly depends on the isolation procedure and the kind of fruit processed. Oil produced by the “Pelatrice” method has a lower monoterpene content and a higher aldehyde and alcohol content than the oil produced during the same time period by “FMC” process. Also, blood oils generally show a higher monoterpene content and a lower alcohol and aldehyde content than blond oils. In addition, early season and late season blond oils have a similar composition. While the amount of the other sesquiterpene hydrocarbons remains practically unchanged, the valencene content increases during the productive season mainly in blood oils. Esters, whose percentage does not reach 0.1%, also increase during the season; however, their content is probably not influenced by the oil isolation procedure or the kind of fruit from which the oil is obtained.