TRA is a national volunteer registry of over 97,000 Australian twins and higher order multiples (e.g., triplets, quadruplets) of all zygosity types and ages. After joining the registry, twins are invited to participate in appropriate and approved studies, with invitations extended to twins depending on study requirements, as well as the profile and interest areas of the twin members. Several sources of recruitment have been utilised, including online registration forms, promotional events, and media advertisements. TRA was formerly known as the Australian Twin Registry, but was rebranded in 2017 to reflect its wider breadth of activities.

Recruitment is ongoing