OBJECTIVE: The term 'missing-middle' has been prominent in discourse relating to provision of mental health care in Australia, particularly by proponents of non-governmental youth mental health services such as headspace and related adult services. We investigate whether there is an empirical basis for use of the 'missing-middle' term, founded on qualitative and quantitative research. CONCLUSIONS: Despite the widespread use of the term 'missing-middle' for advocacy in Australia, there is a lack of research characterising the epidemiological characteristics of the group. The validity of advocacy predicated on the basis of the 'missing-middle' care-gap should be reconsidered. Research, such as systematic service mapping and health needs assessment, is a necessary foundation for evidence-based mental healthcare policy, planning and implementation. Without such research, vital government funds may be deployed to 'missing-middle' programmes that may not improve Australian public health outcomes.