He wants to spend more time with his family.
No more Lord Chancellor
Dr Reid was the Leader of the Commons.
And the historic job of lord chancellor has been scrapped.
Lord Irvine, who was in the job, has retired.
That job involved being both head of the law courts and judges and also a speaker in the House of Lords.
Another politician who quit to have more of a private life is Helen Liddell, who was the Scottish Secretary.
She's replaced by Alistair Darling.