From Haaretz:

Prime Minister Ariel Sharon suffered a “significant” stroke with “massive bleeding” in his brain late Wednesday night, according to a Hadassah University Hospital official, and Sharon’s authority has been transferred to Deputy Prime Minister Ehud Olmert.

In a brief statement outside the Jerusalem hospital, Dr. Shlomo Mor-Yosef said Sharon had suffered “a significant stroke,” adding that he was “under anesthetic and receiving breathing assistance.”

A few minutes later, Mor-Yosef emerged to say that initial tests showed Sharon had suffered a cerebral hemorrhage, or bleeding inside his brain. Addressing reporters in English, Mor-Yosef said Sharon had “massive bleeding and was being transferred to an operating theater.”