In search for several fatty acid with unusual structure in vegetable oils, we have found that unknown peaks were shown on GLC in the analysis of fatty acids of the lipids from the pulp of ripened jujube (Zizypus jujuba var. inermis) fruits. These fatty acids were identified as a series of cis-monoenoic acids with ${omega}-5$ double bond system such as $C_{14:1{omega}5}$, $C_{16:1{omega}5}$ and $C_{18:1{omega}5}$, including ${omega}-7$ fatty acid as $C_{16:1{omega}7}$ and $C_{18:1{omega}7}$, by GLC, solid-phase extraction silver ion-column chromatographic, GLC-mass spectrometric and IR techniques. First of all, total fatty acid methyl esters were resolved into saturated and branched fatty acid, monoenoic acid, dienoic acid, and trienoic acid fraction, respectively, with 100% dichloromethane (DCM), DCM/acetone (9:1, v/v) 100% acetone, and acetone/ acetonitrile (97:3, v/v) solvent system. Unknown fatty acids were included in the monoenoic fraction and were confirmed to have cis-configuration by IR. Picolinyl esters of monoenoic fatty acids gave distinct molecular ion peak and dominant diagnostic peaks, for example, m/z 317, 220 and 260 fragment for $cis-C_{14:1{omega}5}$, m/z 345, m/z 248 and 288 fragment for $cis-C_{16:1{omega}5}$ and m/z 373, m/z 276 and 316 fragment for $cis-C_{18:1{omega}5}$. In this way the occurrence of $cis-C_{16:1{omega}7}$ and $cis-C_{18:1{omega}7}$ could be deduced from the appearance of prominent fragments as m/z 345, 220 and 260, and m/z 373, 248 and 280. Level of total ${omega}-5$ fatty acids amounted to about 30% in the fatty acid composition with the predominance of $C_{16:1{omega}5}$ $ (18.7{sim}25.0%)$, in the semi-ripened and/or ripened samples collected in September 14 ($C_{16:1{omega}5}$ ; 18.7%, $C_{14:1{omega}5}$ ; 3.6% and $C_{18:1{omega}5}$ ; 3.0%), September 22 ($C_{16:1{omega}5}$ ; 25.0%, $C_{14:1{omega}5}$ ; 1.4% and $C_{18:1{omega}5}$ ; 2.6%), and October $7 (C_{16:1{omega}5}$ ; 24.7%, $C_{14:1{omega}5}$ ; 7.7% and $C_{18:1{omega}5}$ ; 2.5%). However, the lipids extracted from unripened jujube in July and August contain these unusual fatty acids as low as negligible. It could be observed that the level of ${omega}-5$ fatty acids in the pulps increased sharply with an elapse of ripening time of jujube fruits. Other monoenoic fatty acids with ${omega}-7$ series, $C_{16:1{omega}7}$ (palmitoleic acid) and $C_{18:1{omega}7}$ (cis-vaccenic acid) could be detected. And in the lipids of the kernel and leaf of jujube, none of ${omega}-5$ fatty acids could be detected.