In 1986, the Centers for Disease Control, in collaboration with the Health Care Financing Administration, surveyed 1350 chronic hemodialysis centers in the United States to ascertain practices associated with the reuse of disposable hemodialyzers and the frequency of pyrogenic reactions and septicemia among patients. Reuse of hemodialyzers was reported by 63% of the centers. Centers that used RenNew-D (n = 5) for reprocessing hemodialyzers, compared with centers that did not reuse (n = 495), were more likely to report pyrogenic reactions (60% vs 13%) and episodes of septicemia (100% vs 55%) among their patients. Reusing hemodialyzers more than 20 times and, in some instances, also using manual reprocessing systems was significantly associated with clustering of pyrogenic reactions regardless of the type of germicide used. To detect membrane leaks developing after multiple reuses, air-pressure-leak tests should be performed on all reprocessed hemodialyzers.