The Bishop of Salisbury, David Stancliffe, has suffered a stroke.
He is being treated in Bournemouth hospital following several days of tests.
Dr Stancliffe was admitted to hospital towards the end of last week.
"Bishop David has suffered a stroke and the hospital is continuing to do tests," said the Bishop of Sherborne, Tim Thornton.
"He has obviously enjoyed visits from his family and is keeping as cheerful as he can."
He added: "Prayers have already been said for him both in the Cathedral and at many other churches where news of his admission to hospital had become quickly known."
The Bishop's family have stressed that the he is unable to receive visitors at the present time.
The Bishop's diary has been cleared for the foreseeable future.
Many of his planned engagements are being carried out by the bishops of Sherborne and Ramsbury.
Dr Stancliffe, 66, is the 77th Bishop of Salibury and was enthroned 15 years ago.