The use of blood cultures to work up fever in postarthroplasty patients was studied retrospectively. Four hundred fifty-three patients done consecutively with a diagnosis-related group 209 discharge diagnosis were studied. One hundred patients (22%) had blood cultures drawn for fever greater than 101°F. Specifically, there were 240 total knee arthroplasty patients with 40 blood cultures drawn. There were 124 total hip arthroplasty patients with 31 blood cultures drawn. One patient with a total knee arthroplasty had positive cultures as did one patient with a total hip arthroplasty. Both were thought to be contaminants, and neither had any sequelae. Blood cultures are expensive and do not add relevant information in the care of postarthroplasty patients.