One of the most common laboratory diagnostic procedures performed in veterinary medicine is the serum biochemistry profile which generally includes data on serum globulin concentration. Identification of elevated serum globulin in a patient should trigger further investigation of this phenomenon by serum protein electrophoresis. Protein electrophoresis gels, whether examined qualitatively or subject to densitometric scanning, provide information on the nature of elevated globulins--in particular whether these are primarily of the alpha, beta or gamma class. The majority of alpha and beta globulins comprise an assortment of proinflammatory proteins, and elevations of these molecules should be expected in any disease state involving an inflammatory process. A number of studies have examined correlations between disease state and concentration of these proteins (in particular C-reactive protein which migrates in the gamma globulin region), but such findings can only be regarded as non-specific indicators of inflammation. Elevation of gamma globulins indicates immune system reactivity and may be polyclonal or monoclonal in nature. By contrast, hypogammaglobulinaemia in an animal with inflammatory or infectious disease might suggest failure of the immunological response (primary or secondary immunodeficiency) and trigger further investigation of this phenomenon. This presentation reviews the causes for hypergammaglobulinaemia in the dog and cat.