An attempt has been made to compare the nutritional quality between naturally occurring conjugated octadecatrienoic fatty acid with trans configuration and the trans fatty acids being produced in hydrogenated fats. The karela seed oil (Momordica charantia) (29.2% trans isomer) was used as the source of conjugated trienoic trans fatty acid and hydrogenated fat for trans fatty acid (39.5%). The two fats were fed to male albino rats (Charles Foster strain) for four weeks. Feeding experiment showed comparable results in terms of growth rate, food efficiency ratio (FER) and serum lipid profile. In the third week the growth rate of rats fed hydrogenated fat with trans showed a significant increase than the karela seed oil with trans conjugated trienoic fatty acid fed group. Total cholesterol level of liver was significantly higher in rats fed karela seed oil containing conjugated trienoic fatty acid with trans configuration. The phospholipid content of heart and brain of rats fed karela seed oil was significantly higher than the hydrogenated fat with trans fed group. © 2004, Japan Oil Chemists' Society. All rights reserved.