Thousands of junior doctors in England are to begin strike action today, with patients being warned to expect major disruption.
Here is a breakdown of what's happening and how it affects you.
When does the strike take place?
It comes into force from 8am on Tuesday, though start times will vary across different hospitals.
It is due to last for 24 hours, during which time the doctors will provide only emergency cover.
How will patients be affected?
Around 4,000 hospital operations and procedures have been cancelled, and thousands more routine appointments are also set to be postponed.
Patients have been asked only to attend A&E in genuine emergencies, and have been warned that hospital services will be under increased pressure.
What can I do if I need non-urgent help?
The NHS is asking patients to make use of its other services while the strike takes place - including GPs practices, walk-in centres, the 111 phone line and pharmacies.
No. A further 48-hour stoppage is due to take place from 26 January, with junior doctors providing emergency care only during this time.
Another planned strike on 10 February is set to see the full withdrawal of labour from 8am to 5pm.
What is the dispute about?
The government is planning a new contract for junior doctos working up to consultant level, saying that the existing deal is "outdated".
The offer currently on the table reflects Health Secretary Jeremy Hunt's desire for a "truly seven-day NHS", and therefore seeks to cut the number of hours on a weekend that junior doctors can claim extra pay.
Under the most recent proposal, doctors would receive an 11% rise in basic pay but extra pay for "unsocial" hours would be cut.
The British Medical Association claims the promise of extra basic pay is misleading due to the changes imposed on pay for unsocial hours, claiming the offer devalues the work doctors do on evenings and weekends.
It also has other concerns about the deal, including protection for doctors working in some specialties.
Hasn't strike action been threatened before?
Yes. In fact, three strikes were called off at the last minute on 30 November after the government, the BMA and the NHS agreed to a continuation of talks instead.
However, after weeks of talks failed to seal an agreement, the strike action is set to take place again barring another 11th hour break in the deadlock.