Tamara Milograd vanished without explanation on the day she left her Newport home in 1971 to visit the Royal Melbourne Show.
Detectives from the Victoria Police Belier taskforce believe she may still be alive and have appealed for public help to solve the mystery. They suspect she could have carved out a new identity and still be living in Melbourne.
The Milograd family's ordeal, stretching almost four decades, is still enough to bring Tamara's 85-year-old mother Luba to tears.
Her brother Nick said the family did everything they could to find her, embarking on "wild goose chases", trips interstate and hiring private investigators.
"We would just like to know that she's all right. My mum still cries about it," he said.
Another brother, Eugene, said the manner of his sister's disappearance did not point to an abduction.
Mr Milograd recalled there were many different unconfirmed leads in the period after the investigation.
There was a sighting at the old Tarmac Hotel in Laverton, a suggestion she had found a job in St Kilda and a rumour she slept in a stable at the showgrounds the two nights after disappearing.
"We'd dearly like her to contact us. Just contact us - say you're all right," Mr Milograd said.
Tamara, who would now be 55, left her family's Mason St home on September 18 to go to the show with a girlfriend.
She never returned and, despite exhaustive inquiries by police and her family, nothing more is known about where she went. Investigators have urged Tamara to contact them, on her terms if she desires.
"All contact between police and missing persons is dealt with in the strictest confidence and is subject to Privacy Act provisions," Victoria Police said.
Belier has been working for the past two years to close up to 600 missing persons cases.
The oldest of the success stories dated to 1960.
The taskforce has also had considerable success with people whose identities remained a mystery after death.
Anyone with information can call Crime Stoppers on 1800 333 000 or visit www.crimestoppers.com.au.