A novel modification of the ferric chloride total serum cholesterol method was evaluated by comparison with the Abell method. The method utilized two premeasured reagents and a filter coupler assembly. Filtration was accomplished by centrifugation into the reaction vial, which also served as its own cuvette. This modification of the ferric chloride determination for total serum cholesterol has been found to be as reliable for clinical use as the Abell method. This judgment is based on accuracy, reproducibility, relative freedom from interfering substances, and ease and time of test performance. This ferric chloride procedure meets all of the acceptance criteria used by Barnett to evaluate cholesterol methods.