1. Clozapine, the first atypical antipsychotic, has demonstrated an efficacy in the treatment of resistant schizophrenia. But one of the major challenge in the treatment of schizophrenia remains the lack of efficacy of antipsychotics on negative symptoms of schizophrenia. 2. The authors studied the efficacy of clozapine in an open study in a population of 51 patients, who met the DSM IV criteria for schizophrenia. Using the positive and negative symptom scale (P.A.N.S.S.), and the Extra Pyramidal Symptoms Rating Scale (E.S.R.S.), we try to identify the specificity of the action of clozapine on the different symptomatic dimensions of schizophrenia. 3. The efficacy of clozapine was clinically significant on the negative symptomatology but was delayed compared to the efficacy on the other dimensions of symptomatology evaluated using the PANSS. 4. Nine patients, were considered as deficit patients; in this sample clozapine also demonstrated a significant efficacy on negative symptoms. The efficacy of clozapine did not seem to be a consequence of the better neurological tolerance of this antipsychotic evaluated with ESRS.