Health bosses are reviewing the future of district general hospitals across the country.
It is a controversial issue. Supporters say it is about providing better care, but critics say it just comes down to saving money.
Reviews are taking place across the country
What is happening?
Reviews into hospital services are happening across England, although they are all at very different stages.
In general, NHS bosses with the backing of ministers are looking at how acute services - that is to say emergency surgery, A&E, cardiac care and critical care facilities which treat the most severely ill - are provided.
There are 175 acute trusts in the health service, running about 250 hospitals providing some or all of these services.
The Tories have identified 29 hospitals which they believe are at-risk.
They say they are run by trusts which have consulted, are already consulting or are rumoured to be about to start consulting on changes.
Many of the consultations already running portray the traditional district general hospital model as outdated, as there is not the money or staff to cover an ever increasing amount of specialist care.
Instead, NHS trusts have started looking at making some hospitals centres of excellence in areas such as heart and cancer care.
The knock-on effect is that some smaller hospitals will face closure or being downgraded by having some of the acute services stripped from them.
Is this being driven by money?
The Tories say there is a "paucity of clinical evidence" and instead financial concerns are driving the changes.
It is true that many of the areas involved are facing financial pressures.
But the hospitals argue they are also motivated by the need to provide care more appropriate to the 21st century.
The government set out a strategy last year to treat more people in the community.
Long-term conditions, such as heart disease and diabetes, have overtaken infectious diseases as one of the biggest burdens on the heath service.
Ministers - and many doctors - argue these conditions could be better managed in community settings by encouraging GPs to set up specialist services or hospital consultants to run clinics in the community.
There is also the issue of the European working time directive which is gradually being phased into the health service.
It means doctors can no longer work the hours they used to - either pacing the wards or on call - and so it is just not possible in a day-and-age when money is tight to employ all the new medics needed to staff specialist services in each hospital.
Some trusts run more than one hospital which replicate the same services, and they argue it makes sense - both clinically and economically, to end this practice.
What do patients think?
Ever since the NHS was set up after World War Two, hospitals have been the service people most closely associate with it.
Whenever, closures or cuts are mentioned, people take to the streets demanding their local hospital remains open.
It has been no different this time. Significant campaigns have been - or are being - mobilised in each area where the idea of cuts have been floated.
Indeed, this remains the trickiest dilemma for NHS bosses. Many will not even speak about cutting hospital services, preferring to use words such as reconfiguration or rationalisation.
What is likely to happen?
Many experts agree the NHS of the future is likely to have fewer acute hospitals.
Instead, specialist care will be provided out of a number of "super" regional centres.
Smaller hospitals will concentrate on the most basic planned surgery, diagnostics and rehabilitation.
They will be supported by a network of community services from extended GP care to physiotherapy centres.
But there is still a long way to go in the process. Many of the proposals have not even been consulted on yet and any major cutbacks will need the agreement of senior health officials.
Which hospitals do the Tories say are under threat?
Chase Farm (London), Frenchay (Bristol), Grantham (Lincolnshire), Horton (Oxford), Huddersfield Royal Infirmary, King George (Essex), Princess Royal (Telford), Royal Surrey County, St Richard's (West Sussex), Worthing and Southlands, Princess Royal (Haywards Heath), Eastbourne, Conquest (East Sussex), University Hospital (Hartlepool), University Hospital Lewisham (London), Queen Mary's (Sidcup), Queen Elizabeth (Woolwich, London), Scarborough General, Trafford General, Hemel Hempstead, Queen Elizabeth (Hertfordshire), Lister Hospital (Hertfordshire), George Elliot (Nuneaton), Hospital of St Cross (Rugby), Warwick Hospital (Warwickshire), Epsom General (Surrey), West Cumberland (Cumbria), Queen Elizabeth (King's Lynn), City Hospital (Birmingham)
Altrincham General was included in the original list, but the Conservatives later said this was an error. They replaced it with Trafford General.