Financial advisor Lynda Spence has not been seen since leaving her parents' home in Glasgow on April 13, 2011.
Her parents, Patricia and James Spence, reported her missing to police a month later.
David Parker, 37, from West Kilbride, Paul Smith, 47, from Largs, Philip Wade, 42, from Glengarnock, all North Ayrshire, and Colin Coats, 42, from Glasgow, are accused of abducting, assaulting and murdering Ms Spence.
The charges against the men allege that on April 14, 2011 they forced Ms Spence into a vehicle in Broomhill Path, or somewhere else in Glasgow, and drove her to a flat in Meadowfoot Road, West Kilbride, where they held her against her will for up to two weeks.
They are accused of gagging and blindfolding her, tying her to a chair with tape and repeatedly punching and kicking her.
Prosecutors also claim the men crushed Ms Spence's toes, burned her hands with lit cigarettes and an iron, cut off her thumb and severed the tip of one of her fingers.
They are also accused of robbing her of a mobile phone and sim card, as well as demanding bank account details and information about financial dealings they believed she was involved in.
Ms Spence, who was 27 when she disappeared, was declared bankrupt at Glasgow Sheriff Court in December 2008 but was discharged the following year.
She was known to use aliases, Lynda Zefaj, Lynda De-bono, Lynda Palmer and Linda Riley.
Coats is alleged to have intimidated Ms Spence, and a man named Seyed Alagha, to extort money from them.
Wade is accused of sending text messages to Ms Spence, threatening her with violence.
All four men face further charges of attempting to cover up the crime by cutting off Ms Spence's head, removing her remains from the West Kilbride flat and destroying, or disposing of, a car and mobile phones.
The Crown also claims that while awaiting trial, Coats asked another inmate at Addiewell Prison in West Lothian to arrange for someone who looked like Ms Spence to attend a solicitor's office to give the impression she was still alive.
In total, Parker, Smith, Wade and Coats face 26 charges, all of which they plead not guilty to.
As the trial got under way at the High Court in Glasgow, judge Lord Pentland told the jury of 10 men and five women to keep an open mind about "each and every issue in the case" and described them as "masters of the facts".
He said: "Your job, ladies and gentlemen, is to decide where or not the charges, allegations, brought against the four accused men have or have not been proved.
"You regard only the evidence which is given under oath."
He warned them not to do any investigations or research of their own.
The trial continues today when the first witnesses are expected to be called.