A&E waits in England are at their worst level for a decade with the four-hour target now being missed - as it is elsewhere in the UK.
Pressures have become so great that a number of hospitals have had to declare major incidents, calling in extra staff, cancelling operations and - in extreme cases - diverting ambulances away from A&E units.
It has led to reports of patients queuing in corridors, being treated in side-rooms and ambulances struggling to drop patients off.
But what is behind these problems? The truth is there isn't one simple answer, but rather a multitude of factors behind the difficulties being seen across the health service.Lack of staff
It has been known for some time that A&E units are struggling to recruit and retain staff.
The College of Emergency Medicines says each unit should have 10 consultants with the largest trusts needing up to 16. But the average number stands at just over seven. There are also said to be shortages of A&E nurses.
Hospitals have reported problems both recruiting and retaining staff withreports emerging of emergency care doctors emigrating abroad.
The college said the "relentless" pressures on A&E units make it unattractive.111 Helpline
The 111 helpline was launched in the spring of 2013 to replace NHS Direct. The idea was to create a system that was integrated better with local health services enabling appointments to be booked.
But it was beset by problems from the start. One of the biggest criticisms has been the fact that it has fewer clinically trained staff than its predecessor.
This, critics say, has led to increases in the number of patients being referred to A&E or an ambulance being called.
Over one in 10 calls end in an ambulance being sent, while one in 13 lead to a patient being sent to A&E. Although, interestingly, in the lead up to the festive period, when calls reached a peak, those figures actually fell.Cuts to social care
While the NHS budget has been rising, the opposite has happened for council-run social care services.
A total of £17.23bn was spent on services for the elderly and disabled last year - down by 3% in five years. It has meant the numbers getting help have been falling - down by 29% to 1.27m during the same period.
This, remember, is at a time when you would expect it to be increasing in light of the ageing population and the fact that people with disabilities are living for longer.
If there is not good access to social care, hospitals can struggle to discharge patients - something that seems to be happening with delays higher in the lead up to Christmas than they were in previous years.GP access getting more difficult
Unlike A&E, waiting times to see a GP are not routinely collected, although there is evidence to suggest it is getting more difficult to see a doctor.
The most recent national GP patient survey found that in the last two years the proportion saying it was not easy to get through on the phone had risen from 18% to 24%. When they did get through 11% were unable to get an appointment.
It comes as both the Royal College of GPs and British Medical Association have been vocal about the workload their members are facing. A recent BMA survey found three quarters of doctors said their caseload was "unsustainable".
The most obvious place patients go if they can't get to see a GP is, of course, A&E.Ageing population
The fact that people live longer has rightly been widely celebrated. One in five people alive today will live to see their 100th birthday.
Over the next two decades the number of over 65s will rise by 50% and the number of over 85s will double.
But this means there are a growing number of frail and elderly people who have complex conditions that take longer to treat.
This is acknowledged to be one of the major causes behind the rise in numbers attending A&E units - and in particular those that needed to be then admitted into hospital for further treatment. Two thirds of emergency admissions are among the over 65s age group.Money is tight
While the NHS budget has been increased - 0.7% a year in real terms on average during this Parliament - money is still short because of the rising demands.
Half-way through the 2014-15 financial year, the NHS in England had racked up a deficit of £630m, with the biggest problems concentrated in hospitals.
A&E units are particularly susceptible when money is tight. Under the funding rules, they can actually be paid less per patient the more they see.
Attempts have been made to correct this anomaly But hospitals still claim it is hampering their ability to cope.
To help A&E units during winter, ministers have released an extra £700m. But £300m of that came in the autumn, which some said was too late to make much of a difference.