The increase in the prevalence of medical errors represents a disturbing trend; hospital-based errors are the eighth leading cause of death in the United States. For the clinical laboratory, errors that occur in the preanalytical phase of testing may account for up to 75% of total laboratory errors; 26% of these may have detrimental effects on patient care, which contribute to unnecessary investigations or inappropriate treatment, increase in lengths of hospital stay, as well as dissatisfaction with healthcare services. This review focuses on these errors, particularly those observed in the preanalytical phase, and how they may affect clinical and financial outcomes. Financial ramifications are also demonstrated through a model that estimates the costs of preanalytical errors for the hospital and laboratory as well as patient care. Copyright © 2013 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.