Tribal leaders from Montana and Wyoming are due to testify during U.S. Senate committee field hearing on the federal government's troubled health program for American Indians.
Representatives of eight tribes are scheduled to appear Tuesday.
Montana Sen. Jon Tester chairs the Senate Committee on Indian Affairs, which has jurisdiction over federal government dealings with 566 American Indian and Alaska Native tribes.
The Democrat is holding the hearing after receiving complaints from the Crow Tribe and others about poor and delayed health care provided by the Indian Health Service.
The agency's acting director, Yvette Roubideaux, also is scheduled to appear.
Tester and U.S. Sen. John Walsh earlier this month asked the U.S. Government Accountability Office to examine problems at the agency's area office in Billings.