An adipocyte membrane glycoprotein, FAT, homologous to CD36, has been implicated in the binding/transport of long-chain fatty acids. FAT/CD36 was identified by reaction with reactive long chain fatty acids derivatives under conditions where they inhibited FA uptake. Expression of CD36 in fibroblasts lacking the protein led to induction of a saturable high affinity, phloretin-sensitive component of oleate uptake. In this report, we have examined the effects of FAT/CD36 antisense expression in 3T3-F442A preadipocyte cells, on FA uptake and cell differentiation. Cells were transfected with pSG5-TAF vector obtained by insertion of antisense coding sequence of FAT/CD36 into the BamH 1 site of pSG5. Four clones were selected based on expression of antisense CD36 mRNA. Levels of CD36 protein were determined by flow cytometry and correlated with rates of oleate uptake. Three clones, TAF13, TAF25, and TAF38 exhibited low CD36 expression and one clone TAF 18 had expression comparable to that of F442A control cells. FA uptake rates in clones TAF13, TAF25 and TAF38 were lower than those observed in TAF18. At confluence, adipocyte differentiation could be promoted by addition of insulin and triiodothyronine only in TAF18 cells but not in TAF13, TAF25 or TAF38. Addition of fatty acids to clones TAF13, TAF25 and TAF38 lead to an induction of CD36 expression, an enhancement of FA uptake and better cell differentiation. The data support a role of CD36 in the membrane uptake of long chain FA. CD36 expression and FA uptake appear to be closely linked to preadipocyte differentiation.