Pre-analytical variables, e.g., specimen collection, transport, and storage, can contribute significantly to inaccurate pH, blood gas, and electrolyte values. The International Federation of Clinical Chemistry (IFCC), through its Committee on pH, Blood Gases and Electrolytes, has developed specific recommendations to minimize the undesirable effects of pre-analytical variables. The Committee has drawn upon the experiences of its own members as well as published data by others. Specifically, the Committee has included pertinent guidelines and suggestions by the IFCC Working Group on Selective Electrodes (WGSE), the National Committee on Clinical Laboratory Standards (NCCLS), and the Electrolyte/Blood Gas Division of the American Association for Clinical Chemistry (AACC). This paper will familiarize the reader with the effect of different types of specimen containers and anticoagulants. It discusses important aspects of specimen collection procedures including patients status and special precautions during specimen collection from indwelling catheters or cannulae. The paper also identifies different requirements in storage and transport of specimens for blood gas and electrolyte analysis.