Introduction. Essential oils represent an increasing economic importance in the citrus by-product industry. Flash vacuum-expansion, a process leading to the disintegration of plant tissues, was applied to the recovery of essential oils from fruits of four Citrus species. Materials and methods. The flash vacuum-expansion process (steam-heating, then rapid introduction into a vessel under vacuum) was applied to peels of lemon, sweet orange, mandarin and grapefruit. Essential oils were recovered with a condenser, then separated by centrifugation. Oil volatile compounds were separated and identified by coupled capillary gas liquid chromatography/mass spectrometry. Results and discussion. Peel essential oil yields were (2.41, 1.43, 0.64 and 0.73) kg × t-1 of fruit for lemon, sweet orange, mandarin and grapefruit, respectively. Oils were enriched in limonene and other monoterpenes, while relative concentrations of monoterpene alcohols (linalool, α-terpineol, β-citronellol, nerol, geraniol) and aldehydes (neral, geranial) were lower in comparison with the volatile compounds of native peels. Conclusion. The flash vacuum-expansion process allowed production of citrus peel essential oils with yields comparable to the Food Machinery Corporation (F.M.C.) process. Oils were enriched in monoterpene hydrocarbons and correlatively impoverished in oxygenated volatile constituents.