Objective: We assessed, from a health sector perspective, options for change that could improve the efficiency of Australia's current mental health services by directing available resources toward ‘best practice’ cost-effective services. Method: We summarize cost-effectiveness results of a range of interventions for depression, schizophrenia, attention deficit hyperactivity disorder and anxiety disorders that have been presented in previous papers in this journal. Recommendations for change are formulated after taking into account ‘second-filter criteria’ of equity, feasibility of implementing change, acceptability to stakeholders and the strength of the evidence. In addition, we estimate the impact on total expenditure if the recommended mental health interventions for depression and schizophrenia are to be implemented in Australia. Results: There are cost-effective treatment options for mental disorders that are currently underutilized (e.g. cognitive–behavioural therapy (CBT) for depression and anxiety, bibliotherapy for depression, family interventions for schizophrenia and clozapine for the worst course of schizophrenia). There are also less cost-effective treatments in current practice (e.g. widespread use of olanzapine and risperidone in the treatment of established schizophrenia and, within those atypicals, a preference for olanzapine over risperidone). Feasibility of funding mechanisms and training of staff are the main second-filter issues for CBT and family interventions. Acceptability to various stakeholders is the main barrier to implementation of more cost-effective drug treatment regimens. More efficient drug intervention options identified for schizophrenia would cost A$68 million less than current practice. These savings would more than cover the estimated A$36M annual cost of delivering family interventions to the 51% of people with schizophrenia whom we estimated to be eligible and this would lead to an estimated 12% improvement in their health status. Implementing recommended strategies for depression would cost A$121M annually for the 24% of people with depression who seek care currently, but do not receive an evidence-based treatment. Conclusions: Despite considerable methodological problems, a range of cost-effective and less cost-effective interventions for major mental disorders can be discerned. The biggest hurdle to implementation of more efficient mental health services is that this change would require reallocation of funds between interventions, between disorders and between service providers with different funding mechanisms.