We have been testing pre-production versions of a system designed by Wyatt Technology Incorporated to facilitate composition-gradient static light scattering measurements. The system, based upon a concept developed previously in our laboratory (see annual reports of the previous two years), consists of a pump module containing three syringe pumps and an inline degasser, and a software package that is used to control the syringes to create composition gradients, to collect data from light scattering and concentration detectors, and to analyze the data in the context of models for equilibrium self-association of a single protein and hetero-association of two proteins. The hardware and software were loaned to us by Wyatt Technology under terms of CRADA DK-05-0104. Preliminary results indicate that with this system one can characterize and quantify equilibrium self-associations of each of two individual protein species and hetero-associations of the two proteins in a single experiment requiring only about 2-3 mg of each protein and less than one hour of data acquisition time.