The concept of negative symptoms is derived from Kraeplin's description of the dissolution of the personality in patients with schizophrenia. Negative symptoms may be either primary, or secondary to positive symptoms, antipsychotic side effects, dysphoric affect and environmental deprivation. Primary negative symptoms represent core features of the illness, and have been termed deficit symptoms. The differentiation of primary from secondary negative symptoms has important treatment implications, as treatment approaches vary greatly for the different types of negative symptoms. Specific pharamacological and psychosocial treatments are available for secondary negative symptoms. However, to date, there are no known effective treatments for primary negative symptoms. The importance of developing effective treatments for primary negative symptoms is underscored by the relationship of these symptoms to poor social, occupational, and global outcome.