SummaryClozapine remains underutilised as the only antipsychotic for treatment-resistant schizophrenia, despite liberal National Institute for Health and Clinical Excellence guidelines for its consideration. Bearing in mind its monitoring requirements and poor tolerability, suggestions are made for patients who fail to improve on other antipsychotic drugs. Clozapine may be offered to apparently unsuitable patients, although this is fraught with difficulty. A realistic appraisal of the alternatives is essential in this situation. Optimising plasma clozapine levels, alongside the use of rehabilitative interventions and adjuncts as necessary, will maximise efficacy, and there are numerous options to minimise side-effects. Clozapine requires a lengthier trial than other antipsychotics and discontinuation should be avoided if possible, as the results are generally very poor. Established successful clozapine treatment can induce substantial functional gains which accrue with time: patients are retained in treatment and relapse is prevented. Such optimal outcomes justify the initial effort expended by all.