Antipsychotic drugs are the main treatment for schizophrenia, helping to treat both the positive symptoms (such as hearing voices, seeing things and having strange beliefs) and negative symptoms (including apathy, tiredness and loss of emotion) of this illness. Selecting the most effective antipsychotic drug that can be tolerated by people with schizophrenia is crucial to successful treatment. Older drugs (also known as typical or first generation antipsychotic drugs), such as chlorpromazine and haloperidol, have been used in treating schizophrenia for over 50 years. Although these older drugs are good at treating the positive symptoms of schizophrenia they tend to cause undesirable side effects. These side effects can mean that people do not tolerate or like taking these drugs, which may lead to relapse and admission to hospital. Since 1988, a newer generation of antipsychotic drugs has become available. These new drugs (known as atypical or second generation antipsychotic drugs) are effective in treating the symptoms of schizophrenia but thought to have less side effects than older drugs. However, although newer drugs may cause less side effects such as movement disorders, they have been linked to other side effects like heart problems or weight gain. Quetiapine is a new antipsychotic drug for schizophrenia that has been available for over a decade. However, it is not clear how the effects of quetiapine differ from older antipsychotic drugs. This review evaluated the effectiveness and tolerability of quetiapine versus older antipsychotic drugs. The review included 43 trials with a total of 7217 people. Most studies were from China. In the main, quetiapine did not differ from older drugs for the treatment of positive symptoms of mental illness. There were also no clear differences in terms of the treatment of negative symptoms. However, it is important to note that evidence from these trials suggests quetiapine causes fewer side effects (such as weight gain, dizziness, movement disorders, the inability to sit still, shaking, tremors and abnormal levels of the hormone prolactin, which can contribute to sexual and mental health problems). However, evidence from the trials is limited due to high numbers of people leaving early in almost all of the studies. More evidence through the completion of well designed studies comparing quetiapine with older antipsychotic drugs is needed.