Objective. This study is planned bringing about a new choice for the prophylaxis of RA spasm which is topical iloprost and compares its efficacy with papaverine and diltiazem. Design. Twenty eight CABG patients with RA grafts were categorized into four groups by taking into account the topical vasodilator ( papaverine, diltiazem, iloprost and saline) that was utilized during harvesting. Arterial segments were separated into four rings and were than soaked with KCL, norepinephrine, phenylephrine and serotonin. Then, acetylcholine was given to induce relaxation and the preparations were put to rest for 10 minute. Results. The contraction response achieved by the vasoreactive agents was most effectively inhibited by papaverine. The effectiveness of the response obtained by iloprost was similar to that of papaverine and significantly stronger than that of diltiazem. Especially at high vasoreactive substance concentrations, diltiazem had a contraction close to that of the control while the protective effect was weaker than those of papaverine and iloprost. Conclusion. Iloprost can be recommended as a strong alternative to the topical agents used for preventing arterial graft spasm.