Compliance has been defined as the extent to which a person's behavior coincides with the medical advice given. Medication compliance is one of the foremost problems affecting neuroleptic efficacy in psychiatric patients. Since chlorpromazine introduction in 1952, antipsychotics are the principal element of schizophrenia treatment. Actually progress links to the use of new antipsychotics are conditioned by quality of compliance. The problem of nonadherence to medication could concern 50% of prescription. The reported incidence of non-compliance with antipsychotic medication ranges from 11 to 80%. In a two thirds of case rehospitalization is the result of complete or partial noncompliance. After one year of first hospitalisation, 40% of relapse results from non adherence to medication. Medication adherence problems increase hospitalisation, morbidity and mortality. Social consequences, professional problems and family troubles linked to hospitalisations lead to low quality of life for patients and high cost for society. There are three main methods of measuring compliance. These include patient and clinical self-report, pill counts, and biological measures. Self-report methods are generally the most cost-effective and time-efficient way of obtaining an indication of compliance. In psychiatric research, the most commonly used self-report measure of compliance is the Drug Attitude Inventory (DAI) originally devised by Hogan et al. On the basis of criticism concerning DAI reliability, a new questionnaire of medication compliance was proposed: the Medication Adherence Rating scale (MARS). The main goal of compliance evaluation is to quantify this phenomenon with accuracy and to find predictive factors of medication nonadherence. Three types of factors influencing compliance are identified: factors due to medications, factors linked to patients and factors depending on the therapeutic relation with the clinician. Tolerance is considered as the principal reason explaining a bad compliance. Neurologic, endocrine and anticholinergic side-effects are the first fact of treatment stop. Medication prescription complexity is although important to take under consideration. Some psychotic's symptoms, comorbid addictive behavior, poor insight are mentioned in the case of noncompliance. Some effective actions to improve compliance are described. Information and communication with the patient, simplification of therapeutic plan, consultation planning and account of side effect are simple and effective actions. Social support is very important for improvement of compliance. The communication attitude of the clinician, therapeutic relation and prescription use are main points of compliance. Compared to a conventional care, psychoeducational programmes of compliance show their superiority. More research on compliance evaluation is needed. Information and tools must be proposed to practitioners.