The most sophisticated testing equipment and skilled technical personnel cannot extract an accurate test result from a blood sample that is drawn, transported, or processed incorrectly. Adapted from a series that originally appeared in Phlebotomy Today-STAT!, this article identifies the most commonly committed preanalytical errors that compromise sample integrity and provides strategies to prevent their occurrence. Topics include blood culture contamination, the order of draw, proper filling and mixing, analyte stability, and centrifugation errors. (7,000 words, 18 pages)