Anorexia is a symptom seen in the majority of patients with cancer or the acquired immunodeficiency syndrome (AIDS) who experience involuntary weight loss. It is frequently not seen as a symptom requiring management in the same proactive manner as pain, nausea, or constipation. Progressive inanition or wasting is a fundamental component of the complex phenomenon known as the anorexia/cachexia syndrome (ACS) of malignancy or AIDS. Weight loss can be seen in the full spectrum of patient care settings: as a presenting complaint, defining condition, treatment-related toxicity, or as a hallmark of impending death. Primary pharmacologic management of ACS includes use of orexigenic agents (appetite stimulants), anticatabolic agents (antimetabolic and anticytokine), and anabolic agents (primarily hormonal). In addition to these specific categories of pharmacologic intervention, broad aspects of symptom management need to be addressed and are complementary. The available literature evaluating pharmacologic management of ACS in both malignancy and AIDS is reviewed.