Lawmakers and health care experts don’t know whether the hospitals, doctors and nursing homes that provide services to the 39 million Americans under Medicare benefits have come to grips with the year 2000 computer problem.

“We remain deeply concerned that many providers still do not appear to be doing all that they must to prepare for the year 2000,” Gary Christoph, chief information officer of the Health Care Financing Administration, which oversees Medicare, said at a House hearing Monday.