Methods for the measurement of the functional concentration of AT III, PLG, and FBG have been developed for the Du Pont aca discrete clinical analyzer. These methods are fully automated, provide excellent reproducibility, and compare favorably with existing methodologies. The availability of these and future coagulation assays on this automated analyzer will provide the hospital laboratory with a reliable means for evaluating hemostatic function. In addition, excellent method reproducibility and use of defined reference standards should significantly contribute to the standardization of coagulation methods.