LAKE JACKSON, Texas -- When Lisa Kelly learned she had leukemia in late 2006, her doctor advised her to seek urgent care at M.D. Anderson Cancer Center in Houston. But the nonprofit hospital refused to accept Mrs. Kelly's limited insurance. It asked for $105,000 in cash before it would admit her.

Sitting in the hospital's business office, Mrs. Kelly says she told M.D. Anderson's representatives that she had some money to pay for treatment, but couldn't get all the cash they asked for that day. "Are they going to send me home?"...