Prostaglandin F 2α inhibits adipose differentiation of primary culture of adipocyte precursors and of the adipogenic cell line 1246 in defined medium. In the present paper, we investigated the effect of FP receptor agonists cloprostenol and fluprostenol on the differentiation of newborn rat adipocyte precursors in primary culture. The results show that cloprostenol and fluprostenol are very potent inhibitors of adipose differentiation. Dose response studies indicate that both agonists are more potent than PGF 2α in inhibiting adipocyte precursors differentiation. 50% inhibition of adipose differentiation was observed at a concentration of 3 × 10 −12 M for cloprostenol and 3 to 10 × 10 −11 M for fluprostenol respectively whereas the PGF 2α concentration required to elicit the same effect was 10 −8 M. In contrast compounds structurally related to PGE 2 such as 17-phenyl trinor PGE 2 had no effect on adipose differentiation except when added at a 10,000-fold higher concentration.