We compared contamination rates of blood cultures obtained either from newly inserted intravenous catheters or via venipuncture. Of 2,431 blood cultures, the overall contamination rate was 2.7% (intravenous catheter, 3.4%; venipuncture, 2.0%; P=.043). The site of lowest contamination was the antecubital fossa, making this the optimal choice for blood-culture sampling.