Pemetrexed (Alimta, Eli Lilly and Company, Indianapolis, IN) is a structurally novel anti-folate agent. The United States Food and Drug Administration has approved pemetrexed for the treatment of patients with malignant pleural mesothelioma and previously treated patients with locally advanced or metastatic non-small cell lung cancer. In the phase III trials that led to its approval, rash was reported in 17 and 22% of patients receiving pemetrexed alone or in combination with cisplatin. However, little has been published about the characteristics of this rash or about its mechanism. In an attempt to contribute to the growing body of knowledge about this new agent, we describe a case in which a patient developed a rash secondary to urticarial vasculitis associated with pemetrexed.