Oxidative stress and antioxidant enzyme activities after starvation of Oncorhynchus mykiss larvae were studied. Just after yolk-sac absorption, free-swimming larvae were maintained under starved condition for a period of 21 days. Sampling of fish were carried out every week and their whole bodies were used for the analysis of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSHpx), glutathione reductase (GR), glutathione S-transferase (GST) and also analysis of malondialdehyde (MDA) and glutathione (GSH). Antioxidant enzymes activities showed that GST and CAT had the highest activity, whilts SOD and GSHpx had the lowest activity of all the enzymes assayed in 14 day free swimming starved larvae. SOD activity were reached to the peak in free swimming larvae before the appearance of higher level of MDA in 7 day starved larvae. The level of MDA was significantly higher in 7 day starved larvae and significantly lower in 14 day starved larvae. Sigma PUFA and Sigma n-3 fatty acid have the highest level in 7 day starved larvae and lowest level in 14 day starved larvae. After the free swimming larvae, there was a significant decrease in vitamin E (alpha-tocopherol and delta-tocopherol) level in all starved larvae.