Till date, many workers have demonstrated the nutritive value of dietary lipids and the qualitative and quantitative requirements for essential fatty acid (EFA) in many cultivable fish. From the data accrued, a categorization can be made for the EFA requirement as follows: Type I (require n-6 fatty acids), Type II (require both n-6 and n-3 fatty acids) and Type III (require n-3 fatty acids). Common carp Cyprinus carpio and grass carp Ctenopharyngodon idella are codified as Type II fish based on their EFA needs. The requirement of both fish for dietary n-6 and n-3 fatty acids is found to be 1% and 0.5-1%, respectively. Our recent experiment clearly indicated that grass carp fed diet without EFA show deficiency symptoms like vertebral column curvature (VCC), indicating lordosis. The manifestation is similar to SEKOKE DISEASE which is characterised by apparent muscular dystrophy. However, grass carp fed an EFA-deficient diet did not exhibit the apparent muscular dystrophy. Recently, we have also investigated the interaction between EFA and vitamin E (VE), and the metabolism of linoleic acid (LA) using the isotope technique. These results are to be reviewed.