Response surface methodology (RSM) was used to determine optimal conditions for the lipase-catalyzed enrichment of hazelnut oil by incorporating n-3 PUFA from menhaden oil. A four-factor, five-level central composite design was used, and hazelnut oil containing n-3 PUFA was successfully produced. The effects of incubation time, temperature, substrate molar ratio, and water content on the incorporation ratio were investigated. From the evaluation of response surface graphs, the optimal conditions for incorporation of long-chain n-3 PUFA into hazelnut oil were identified as 45-60 degrees C for temperature, 30-40 h for reaction time, 1:1-2:1 (mol hazelnut oil/mol menhaden oil concentrate) for substrate molar ratio, and 3-5% (w/w) for water content. Experiments conducted at optimized conditions predicted by the model equation obtained from RSM yielded structured lipids with 19.6% n-3 PUFA. This value agreed well with that predicted by the model. This structured lipid containing PUFA may be nutritionally more beneficial than unmodified hazelnut oil.