Controversial 'right to die' laws are to be debated in parliament today for the first time in almost 20 years.
Labour MP Rob Marris will introduce the Assisted Dying Bill after coming top of the Private Members' Bill ballot following the general election.
The legislation, which passed an initial vote in the House of Lords last year but failed to become law, is a first key question of conscience for the new House of Commons.
Mr Marris said his Bill was about offering people "choice and dignity".
In a blog post ahead of the debate, the Wolverhampton South West MP said: "With appropriate, strong safeguards, terminally ill adults of sound mind should be legally allowed to choose to have assistance to end their own lives."
I value life, and I do understand that some people believe very deeply that ending one's own life is always wrong. Nevertheless, the depth and sincerity of their belief should not mean that they deny choice to those of us who do not share their beliefs.
Last month, ITV News travelled with British right to die campaigner Bob Cole to Dignitas in Switzerland where he ended his life after learning he had terminal cancer.
A year before, his wife Ann, who had Parkinson's Disease, had ended her life in the same clinic.
His final wish was for a change in UK law that bans assisted suicide.
A Commons vote on the right to die has not been held since 1997.
MPs have a free vote on the issue which is set to break across party lines with opposition on both sides of the Commons.
Former GP and Tory MP Sarah Wollaston said she would not back the legislation, adding: "For all the Bill's supposed safeguards, once we cross the line to allow medically assisted dying we risk ending up in a very different place and with very different attitudes to the value of life."
Prime Minister David Cameron is to miss the free vote as he attends regional visits but he has made it known he would oppose a bill.
The Prime Minister has made his views clear on this issue before. He is not convinced that further steps need to be taken and he is not in favour of an approach that would take us closer to euthanasia.
A similar Bill, introduced by Lord Falconer, was granted a second reading by the House of Lords following a marathon and impassioned debate last year.
It was subject to two days of detailed committee stage debate but failed to make progress before the election.
What does the Bill propose?
Two doctors and a High Court judge would have to be satisfied of the requesting patient's eligibility
The right to die would only be granted for those terminally ill with less than six months to live who are mentally fit to make the decision and aware of alternatives
What will happen to the Assisted Dying Bill?
Mr Marris' Bill is controversial so it is likely to spark a fierce debate in the Commons today but enough MPs are likely to be present to ensure a second reading vote takes place
At least 100 MPs will need to be present to vote for a closure motion to end the debate and force a division before 2.30pm
If a closure motion is not passed, opponents of the Bill could try to stall its progress by filling up the debate time with lengthy speeches, a tactic known as Filibustering
If the Bill does win a second reading today, as backbench legislation it can only be considered on a small number of Friday sittings of the Commons but will still need to go through all the normal legislative stages