Adherence to treatment is a general indicator of quality and success of communication between the physician and the patient. It means the extent to which patient behaviour, in terms of taking medications, following diets, or executing life-style changes, coincides with medical or health advice. Nonadherence to antipsychotic therapy in patients with schizophrenia is far more widespread than clinicians assume. Lower nonadherence in therapy based on antipsychotics of the second generation compared with conventional medications has already been indicated by early reports. The consequences of nonadherence include exacerbation of symptoms, an increased relapse rate, psychiatric hospitalization hospitalisation, and less favourable patient prognosis. There are several factors that cause treatment nonadherence in schizophrenia: causes derived from the schizophrenic disorder itself, patient characteristics, causes associated associated with the health-care system, and the antipsychotic treatment itself.