The determination of serum total proteins by biuret reaction is subject to severe lightscattering interference in the presence of elevated triglycerides. In addition, the dilution effect due to the voluminous character of certain lipoproteins creates an apparent diminished concentration of the serum proteins. The spectral distortion from turbidity is so dramatic that the sample must be subjected to preliminary treatment in order to remove the interference before the biuret reaction can be attempted. In opposite fashion the negative error caused by the dilution effect tends to counteract the positive error caused by the light scattering. However, these two somewhat compensating errors are not equal and the overall result is invariably a falsely elevated concentration. Ultracentrifugation or extraction with the simultaneous precipitation of all proteins is recommended but both approaches obviously require a separate preliminary treatment prior to carrying out the total protein assay and may be quite clumsy. Another miscellaneous method such as sample blanking appears to be somewhat ineffective when turbidity is severe. In comparison to the other clarifying techniques, a procedure involving removal of the turbidity by lipolytic action with entrapment of the liberated fatty acids as a transparent nonmeasuring complex would appear to be a simpler and more convenient procedure for routine use and that alternative is what is described here. An additional benefit to this modification is the maintenance of essentially the same procedural steps and reagent composition as the recommended candidate reference procedure. 1993 Academic Press. Inc.