This study was carried out to separate and identify the acidic compounds in tobacco leaves. Izmir tobacco leaves was extracted with isopropyl ether and the extract was concentrated. The concentrate was extracted with 6% NaHCO3 aqueous solution. The aqueous extract was acidified with sulfuric acid, and extracted with diethyl ether. The acidic material was fractionated on silicic acid column using a benzene-methanol mixture with a stepwise increasing methanol concentration. The resulting fractions were esterified with diazomethane, and then identified by GC, GC/MS using SPB -5 fused silica capillary column. Most of acidic compounds in Izmir tobacco leaves were elected from fraction B which was benzene-methanol(98 : 2) mixture on silicic acid column chromatography. The identified acidic compounds of Izmir tobacco leaves were 18 saturated acids, 8 unsaturated acids, 5 dicarboxylic acids, 13 aromatic acids and 7 terpenoid acids. The major acidic compounds of lzmir tobacco leaves were 2- methylbutanoic, 3-methyl butanoic, 3- methylpentanoic, hexanoic, nonanedioic, phenylacetic, benzoic, 4- methoxybenzoic, 3, 5- dimethoxybenzoic, methoxycinnamic and 3, 4- dimethoxycinnamic acid. Key Words : Izmir tobacco, Acidic compounds, GC/MS.