In the last 2 decades the introduction new biologic agents such as tumor necrosis factor alpha inhibitors has resulted in potent disease modifying effects in a variety of immune-mediated diseases. In addition, there were major advancements in cancer treatment due to chemotherapeutic agents including granulocyte macrophage-colony-stimulating factor, interferon, epidermal growth factor receptor inhibitors, and kinase inhibitors for the treatment of hematologic malignancies as well as solid tumors. However, a variety of toxicities including cutaneous reactions is seen in association with these agents. Awareness of commonly associated skin toxicities and recognition of corresponding histologic features is of importance.