Of 33,111 patients admitted to a large hospital in Vietnam from November 2000 through July 2001, a total of 303 were undergoing hemodialysis and had pyrogenic reactions (ie, fever and/or rigors). Ten case patients (3.3%) had documented bacteremia; pathogens were largely waterborne microorganisms. Pyrogenic reactions in case patients might have occurred because of suboptimal water quality or inadequate dialyzer reprocessing procedures.