Lambs (n = 48) were used in a 2 x 2 factorial arrangement oftreatments to evaluate effects of inclusion of oil containingPUFA in high-concentrate diets (with or without) and durationof oil supplementation (pre- vs. postweaning) on CLA concentrationof muscle and adipose tissue. Lambs were fed preweaning creepdiets (with or without oil) corresponding to the dietary lactationtreatment diet (with or without oil) of the dam. Dams blockedby lambing date and rearing type were randomly assigned to 1of 2 lactation dietary treatments with or without oil supplementation.Creep diets contained approximately 70% concentrate and 30%roughage and were provided to lambs for ad libitum intake. Atweaning (58.7 ± 2.5 d of age), lambs (n = 48) were randomlyassigned within preweaning treatment groups to 1 of 2 postweaningdietary treatments (with or without oil) and 16 pens in a randomizedblock design, blocked by sex and BW. Postweaning diets wereformulated to contain approximately 80% concentrate and 20%roughage and were fed once daily for ad libitum intake. Soybeanand linseed oil (2:1, respectively) replaced ground corn andprovided 3% additional fat in pre- and postweaning diets. Lambswere slaughtered at 60.3 ± 4.2 kg of BW. A subcutaneousfat (SQ) sample was obtained within 1 h postmortem and a LMsample at the 12th rib was obtained 24 h postmortem, and bothwere analyzed for fatty acid profile. Feedlot performance andcarcass measurements were not affected (P >=0.26) by oil supplementation.Total CLA content of LM and SQ was not affected (P >=0.08) byoil supplementation pre- or postweaning, but trans-10, cis-12CLA was greater (P = 0.02) in SQ from lambs supplemented withoil postweaning. Total PUFA content in LM was greater (P = 0.02)in lambs supplemented with oil pre- or postweaning as a resultof increased concentrations of 18:2cis-9, cis-12 and longerchain PUFA. Conversely, pre- and postweaning oil supplementationresulted in less (P = 0.04) MUFA content in LM. Only postweaningoil supplementation increased (P = 0.001) SQ PUFA content. Feedingoils containing PUFA to lambs pre- and postweaning did not increaseCLA content of muscle, whereas postweaning oil supplementationminimally increased CLA concentration of SQ fat. Inclusion ofsoybean and linseed oil in pre- and postweaning diets increasedtotal PUFA content of SQ fat and muscle tissue without adverselyaffecting growth performance or carcass characteristics.