The present study was conducted to evaluate the effect of different dietary lipid sources, age and sex on the SFA and MUFA metabolism in broiler chickens using a whole body fatty acid balance method. Four dietary lipid sources (palm fat, Palm; soyabean oil, Soya; linseed oil, Lin; and fish oil, Fish) were added at 3 % to a basal diet containing 5 % Palm. Diets were fed to female and male chickens from day 1 to either day 21 or day 42 of age. The accumulation (percentage of net intake and ex novo production) of SFA and MUFA was significantly lower in broilers fed on Palm than in broilers fed on the other diets (85·7 v. 97·4 %). Conversely, β-oxidation was significantly higher in Palm-fed birds than the average of the other dietary treatments (14·3 v. 2·6 %). On average, 33·1 % of total SFA and MUFA accumulated in the body were elongated, and 13·8 % were Δ-9 desaturated to longer chain or more unsaturated metabolites, with lower proportions being elongated and desaturated for the Palm and Fish diets than for the Soya and Lin diets. Total in vivo apparent elongase activity decreased exponentially in relation to the net intake of SFA and MUFA, while it increased with age. Total in vivo apparent Δ-9 desaturase activity was not significantly affected by dietary treatment or age. Total ex novo production and β-oxidation of SFA and MUFA showed a negative and positive curvilinear relationship with net intake of SFA and MUFA, respectively. Sex had no effect on SFA and MUFA metabolism.