Double-lumen central venous access (CVA) catheters are occasionally used in pharmacokinetic studies for drug administration and blood sampling. The samples are often collected by the nursing staff and thus the investigator may not be aware of the specific sampling technique used. We present an example of the dramatic effect that an incorrect sampling technique from double-lumen CVA catheters can have on pharmacokinetic outcomes. Using a double-lumen Hickman catheter (Poly-Cath Central Venous Catheter; Strato Medical Corporation/Infusaid Inc., Manchester, GA, U.S.A), sampling during the infusion can be performed when the infusion is connected to the lumen with the end most downstream and blood is collected from the proximal opening. With a normal double-lumen catheter, sampling can only be performed by briefly interrupting the infusion or after the infusion.