During the past decade, evidence from research on mood disorders has demonstrated that remission is the optimal outcome of treatment. However, there continues to be considerable variability in the specific characteristics that are accepted as indicators of remission. Increasing knowledge of mood disorders and their underlying mechanisms may allow for the development of a new diagnostic and assessment system that no longer is based solely on symptoms and other descriptive phenomena. Continued advances in neuroscience may allow for more knowledge of the underlying neurobiological status and more accurate assessments of the underlying disease state and response to treatment, thus enabling physicians to use treatments that will most effectively bring patients back to euthymia and a truly disease-free healthy state. Until then, remission should continue to be based on the descriptive and experiential phenomena of symptoms and psychosocial functioning.