Diagnosis and management of adverse drug reactions constitutes a significant portion of U.S. health care costs. The clinical presentation of these reactions varies from self-limited, morbilliform drug eruptions to more severe, systemic reactions, such as drug hypersensitivity syndromes, Stevens-Johnson syndrome, and toxic epidermal necrolysis, which are associated with significant mortality. The role of the consulting dermatologist is to expeditiously and effectively recognize and classify these drug reactions on the basis of patient histories and awareness of the dermatologic literature as it pertains to the rates of and risk factors for adverse cutaneous events associated with use of numerous medications. This combined with a systematic approach to the workup of a patient with a suspected drug eruption allows for prompt recognition, classification and treatment of these unforeseen events.