The aim of the present work was to investigate the effects of trans-10,cis-12 conjugated linoleic acid (CLA) on the activity and expression of lipogenic enzymes and lipoprotein lipase (LPL), as well as on the expression of transcriptional factors controlling these enzymes, in adipose tissue from hamsters, and to evaluate the involvement of these changes in the body fat-reducing effect of this CLA isomer. Thirty male hamsters were divided into three groups and fed atherogenic diets supplemented with 0 (linoleic group), 5 or 10 g trans-10,cis-12 CLA/kg diet, for 6 weeks. Body and adipose tissue weights, food intake and serum insulin were measured. Total and heparin-releasable LPL and lipogenic enzyme activities (acetyl-CoA carboxylase (ACC); fatty acid synthase (FAS); glucose-6-phosphate dehydrogenase (G6PDH); and malic enzyme (ME)) were assessed. ACC, FAS, LPL, sterol regulatory element-binding proteins (SREBP-1a), SREBP-1c and PPARgamma mRNA levels were also determined by real-time PCR. CLA did not modify food intake, body weight and serum insulin level. CLA feeding reduced adipose tissue weight, LPL activity and expression, and increased lipogenic enzyme activities, despite a significant reduction in ACC and FAS mRNA levels. The expression of the three transcriptional factors analysed (SREBP-1a, SREBP-1c and PPARgamma) was also reduced. These results appear to provide a framework for partially understanding the reduction in body fat induced by CLA. Inhibition of LPL activity seems to be an important mechanism underlying body fat reduction in hamsters. Further research is needed to better characterize the effects of CLA on lipogenesis and the role of these effects in CLA action.