Coagulometers perform the common screening tests prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time, and Clauss fibrinogen, and most also perform chromogenic and immunoturbidimetric assays. Before implementation of an analyzer in the laboratory, selection criteria and various considerations should be reviewed and market research performed in order to arrive at the appropriate instrument selection for the laboratory. The laboratory should first perform a brief on-site evaluation of the instrument, which includes a safety evaluation, limited staff training, and preliminary performance assessment. A more detailed method evaluation will include studies of comparability, imprecision, on-board reagent stability, carryover, interfering substances, and efficiency for clot-based, chromogenic, immunoturbidometric, and D-dimer assays.