Development of centrifugal analyzers capable of making light-scattering measurements has prompted the investigation of the application of this type of instrumentation to the measurement of specific proteins. Investigation of antigen/antibody complex dimension and the kinetics of the IgG/anti-IgG reaction as followed by light scattering are examined in relation to improved analytical methodology. The effect of nonspecific protein on the reaction rate has been investigated for IgM, and data are presented that provide insight into the mechanism of the effect of periodic mixing.