Benefits of cancer treatment must assess quality as well as quantity of survival. Recently, researchers have attempted to define and measure quality of life (QL). Reliable QL measures are useful for rating the QL costs of cancer itself, for rating existing cancer treatments and therapies under clinical investigation, and for evaluating the effectiveness of interventions to improve or prevent deterioration in QL status. Collaborative decision making by patients with their oncologists about anticipated therapy is enhanced by consideration of QL risks. Measures have broadened from assessing only performance status to include the domains of physical status (activity level, cognition, sexuality, fertility, and symptoms of pain, nausea, vomiting), psychological status (sense of well-being, depression, anxiety), social interaction (with sexual partner, family, friends, and co-workers), and economic status. Studies applying these concepts to patients who are survivors, in curative treatment, in palliative treatment, and terminally ill will be discussed.