Between February and June 2006, Human Rights Watch and the Association for the Promotion of Human Rights and Detained Persons conducted an investigation into the detention of insolvent hospital patients in Burundi. Of 11 hospitals visited, nine were found to be holding former patients in detention for being unable to pay their hospital bills. Thirty-seven detained patients, and key informants in government, hospital administration and health services, were interviewed. The detention of insolvent hospital patients was described as a routine practice, dating from the 1990s. Conditions of detention included overcrowding, insufficient food and water, and withholding of further medical treatment. Seventy-two per cent of patients interviewed had been detained for 1 month or longer at the time of interview. Mechanisms designed to exempt or reimburse the health fees of low-income and indigent people failed to protect patients from becoming detained. The detention of insolvent patients is a clear violation of rights established under international law, including the right not to be arbitrarily detained or detained as debtors and the right to accessible health care. The abolition of user fees for women giving birth and for small children in May 2006 has reduced the number of detained patients, but in June 2006 we visited two hospitals and found 77 detained men, older children and women with other health problems. Burundi, with the support of the international community, must immediately stop the detention of patients and address the urgent financing needs of health facilities.