Health bosses admit they are cancelling up to 20 operations each week in Brighton because of an "unprecedented" accident and emergency crisis.
Hospitals in East and West Sussex say they are also facing the hallmarks of chaotic winter demands and are struggling to cope.
Some of the problems include severe accident and emergency waits, older people stuck in hospital because there are no care home places and routine operations put on hold.
Hospitals said they are being severely hampered by the ongoing, chronic lack of care home places where patients could go after hospital treatment.
There has also been a rise in emergency admissions.
Brighton Health Care NHS Trust, which runs four hospitals in the town, has cancelled 241 operations in the past three months alone, nearly twice the figure for the same time last year.
Trust chief executive Stuart Welling said patients were also facing "horrendous" waits in accident and emergency.
He explained patients at a new casualty unit at the Royal Sussex County Hospital, Brighton, where the sick and elderly waited in beds rather than on trollies while doctors admitted them, were ex-periencing 36-hour delays instead of the predicted six-hour waits because there were no vacancies.
He said the problem of older people having to stay in hospital simply because there was nowhere else for them to go was, at its worst, putting vulnerable patients at risk of infection.
Social Services departments across Sussex have faced ongoing cash shortfalls which make it harder for them to fund care homes. Health and Social Services bosses have agreed to work more closely to ease the impact on hospitals.
Mr Welling said: "The hospitals have been under exceptionally high pressure. There has been no respite and a number of days when we have had no available beds.
"What we're seeing is a real inability to reduce waiting times for routine surgery because we're having to move people further and further down the list.
"There is a general recognition this is a total health and social care problem that needs to be resolved."
Pam Lelliott, a spokeswoman for Worthing Hospital, said it was also running to full capacity - usually a winter problem.
At Eastbourne District General Hospital, the 30-bed Seaford 2 ward, usually used for elective orthopaedic patients, is now housing general medical cases because of bed shortages.
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