This guideline specifies recommendations on how to plan and execute the selection, evaluation, validation, and implementation of a laboratory coagulometer. It includes assessment of safety, carryover, precision, bias, linearity, and comparability for coagulometers that perform clotting, chromogenic and/or immunoturbidimetric and/or chemiluminescent testing on plasma. The intended users of this guideline are hospitals, reference laboratories, and manufacturers. It is intended as a guideline for evaluation of commercially available coagulometers that have received prior US Food and Drug Administration 510(k) clearance, CE mark, or other country-specific registration. This guideline is not intended for use by facilities evaluating point of care or manufacturers of point-of-care coagulometers. For information on point-of-care coagulometers, refer to CLSI/NCCLS document H49.1 It also is not intended to provide guidance for platelet testing or the completion of 510(k) clearance documentation, nor intended to proscribe the level of customer service provided by vendors. This guideline recommends the selection of tests and procedures to validate the performance of coagulometers, but it does not address the process to validate each test method of the device. This guideline is not intended to replace any existing standards or requirements but should be used in addition to existing standards.