There are more than 7,000 people currently on the waiting list for an organ transplant; but last year, only 3,000 operations were carried out.
Every day in the UK, three people die while waiting for a donor organ.
All this week ITV News will be following doctors and patients at Papworth Hospital in Cambridgeshire which specialises in heart and lung transplants.
ITV News Medical Editor Lawrence McGinty reports from Papworth where he met Alex Smith who has recently had a heart transplant and Richard Worthington who has had his transplanted heart for almost three decades:
Vincenzo has been transformed from a patient so sick he could not wash his face to a man who strides confidently with a gleam in his eye.
A look at organ donation rates around the world and how the UK compares.
In a one hour special the Tonight programme investigates the lives of the 10,000 Brits on waiting lists for an organ transplant.