Three Scottish police forces have launched a new investigation into the unsolved murders of seven young women dating back almost 30 years.
The World's End pub murders are being investigated
The inquiry was launched after what police described as a "significant scientific breakthrough".
The cases include Edinburgh's notorious 1977 World's End pub murders.
The man leading the inquiry, involving the Lothian and Borders, Strathclyde and Tayside forces, said there were strong links between the deaths.
Lothian and Borders Deputy Chief Constable Tom Wood said: "The advances in DNA have given us information we could never have imagined in the past.
"Whereas we had suspicions that these cases might be connected we could not be certain.
Anna Kenny, August 1977
Matilda McAuley, October 1977
Helen Scott and Christine Eadie, October 1977
Agnes Cooney, December 1977
Carol Lannan, March 1979
Elizabeth McCabe, March 1980
"Now we believe that they may be and that gives us a clear route to follow with the strong hope that we will track down the killer(s) of these women, even though almost 30 years have passed."
Asked if police were hunting a serial killer, Mr Wood said: "We're not saying we are looking for one person.
"We're saying that we now realise that, although over the years there's been a lot of speculation about links between these crimes, we're now in a position to suggest, or believe, that there may be strong links between these crimes.
"So much so that we are taking these steps of forming this joint inquiry."
Last year Lothian and Borders Police launched a website to help their investigation into the World's End murders.
The bodies of 17-year-olds Helen Scott and Christine Eadie were found in separate spots six miles apart in East Lothian in October 1977.
They had been beaten, raped and strangled after disappearing during a night out at the pub on Edinburgh's Royal Mile.
The killer or killers have never been found, despite one of the largest murder inquiries ever carried out in Scotland.
The other victims were Anna Kenny and Hilda McCauley, who were both killed in Glasgow in 1977.
Agnes Cooney's body was found in Lanarkshire later that year, while Carole Lannan and Elizabeth McCabe were murdered in Dundee in 1979 and 1980 respectively.
A police spokesperson said the new information had produced a positive line of inquiry.
Teams of officers from each force have begun a major analysis of the information gathered in connection with the cases.
It is expected that this "painstaking process" will take some months.
Mr Wood said officers would be keeping in touch with the victims' families.
"You cannot describe, I don't think, the anguish that they have been through over this long period of time," he said.
He renewed an appeal for anyone with information to contact police.
"What I would like to say to all members of the public is we still need your information, it's still valuable," he said.
"Don't assume that little bit of information you have is worthless because of the marvels of forensic science.
"It's still crucially important that we get members of the public giving us information."