Up to a third of patients with schizophrenia develop treatment resistance. Clozapine has been established as the most effective antipsychotic medication for treatment-resistant schizophrenia. However, it is significantly underutilised in this population. Possible reasons include clinicians' lack of experience with the drug and negative attitudes towards it. African-Caribbean patients are less likely to be treated with clozapine compared with their White counterparts and more likely to have treatment discontinued due to perceived risk of agranulocytosis. This paper discusses the current evidence relating to the underuse of clozapine and factors responsible for this.