The essential oil constituents of mandarin (Citrus reticulata Blanco) grown in Burundi were extracted by cold-pressing method and analyzed by GC and GC/MS. Fifty-eight constituents, amounting to 97.2% of the total volatiles were identified. Monoterpene hydrocarbons accounted for the most abundant chemical group (94.7%). Limonene was the most prominent constituent (84.8%), followed by gamma-terpinene (5.4%), myrcene (2.2%) and alpha-pinene (1.1%). Sesquiterpene hydrocarbons accounted for a minor quantity (0.2%), where germacrene D and valencene were the main constituents. Oxygenated compounds of various chemical groups constituted 2.3%. Aliphatic aldehydes (0.7%) and terpene alcohols (0.7%) were the major chemical groups. The main constituents were linalool (0.7%), octanal (0.5%) and decanal (0.2%). Octyl acetate, alpha-sinensal, decanol and perillaldehyde occurred at 0.1% levels. Thymol, alpha-sinensal, methyl thymol, and the acetate esters, bornyl, alpha-terpinyl, geranyl, citronellyl and decyl acetates were detected, each at < 0.05%.