Idiopathic pulmonary arterial hypertension is a rare but serious and life-threatening disease that leads to right heart failure and death within 2.8 years without specific treatment. This review focuses on the stable prostacyclin analog iloprost, its biologic action and pharmacology and, finally, on its clinical development, efficacy and safety in patients with idiopathic pulmonary arterial hypertension, which led to its approval for this indication. Furthermore, this review assesses the role of iloprost compared with other newly developed drugs, such as the endothelin receptor antagonist bosentan and the phosphodiesterase-5 inhibitor sildenafil, as well as other modes of application of prostacyclin and its analogs for the treatment of idiopathic pulmonary arterial hypertension. Based on the different modes of action of these substances, a combination of these treatments could be most promising for the future.