To characterize the thromboxane A2/prostaglandin H2 (TXA2/PGH2) receptor on baboon platelets the binding of [125I]BOP was studied. [125I]BOP bound to washed baboon platelets in a saturable manner. Scatchard analysis of binding isotherms revealed a Kd of 1.12 ± 0.08 nM and a binding capacity of 54 ± 5 fmoles/109 platelets (326 sites/platelet). Several TXA2/PGH2 agonists and antagonists displaced [125I]BOP from its baboon platelet binding site with a rank order of potency similar to human platelets: I-BOP > SQ29548 > U46619 = I-PTA-OH. I-BOP aggregated washed baboon platelets with an EC50 of 10 ± 4 nM. The results indicate that [125I]BOP binds to the TXA2/PGH2 receptor on baboon platelets and that this receptor is similar to its human conterpart.