After drawing blood for culture, medical students and house officers are often taught to change needles before inoculating the culture media. Data to support this practice have been scarce. We obtained simultaneous blood cultures on 75 hospital patients using two techniques: changing needles (C) or not changing needles (NC) before inoculating the cultures. Positive cultures judged to be contaminants were obtained in 4/75 patients in the NC group (5.3%) and in 1/75 patients in the C group (1.3%). This difference was not statistically significant. The practice of changing needles after drawing blood for culture may not be necessary, thus reducing the risk of needlestick injury.