In recent years, nursing homes and other healthcare providers have turned increasingly to group purchasing organizations to improve their purchasing capabilities. But these organizations are facing growing scrutiny. Powerful senators from several committees recently sent letters to leading GPOs. The correspondence demands detailed information about service and reimbursement practices. The implicit allegation is that GPOs are inflating costs and contributing to healthcare fraud, a charge that GPOs vehemently deny. As both sides dig in, look for heated hearings in Congress later this year.