Despite a better overall tolerance as compared to classical antipsychotics, atypical antipsychotics are not devoid of side-effects, notably metabolic factors (weight gain, alteration of lipid and glucose profile). These side-effects are very troubling concerning long term morbidity and mortality and may also influence compliance towards drugs. The department of psychiatry of the Hospital University Centre has established a guideline on the clinical monitoring of patients receiving atypical antipsychotics, based on recently published consensus, which will be presented here. In addition, recent studies show that weight gain and metabolic alterations induced by this type of medication may be influenced by the genetic background of the patients. Such studies should allow, in the near future, to adapt the treatment for each patient.