The changed electrophoretic patterns, glycoproteins, mucoproteins, "inflammation units," and serum enzymes in arthritic rats also occurred in other inflammatory conditions. Significant changes in total protein, blood glucose, amino acid nitrogen, free fatty acid, lactic acid, and serum clolesterol did not occur, but the serum complement levels were elevated in arthritic rats. Most of the changes occurred 2 to 6 days after the intradermal inoculation of adjuvant. However, the outward manifestations of arthritis did not develop until the 13th day. Procedures to determine nonspecific in-flammation units in blood plasmas of rats and other species were described. These inflammation units increased in certain inflammatory diseases. Studies of electrophoretic patterns, glycoproteins, mucoproteins, inflammation units, and enzymes (lactic dehydrogenase, isocitric dehydrogenase, and glutamic oxalacetic transaminase) in the exudates and serums of rats with artificially induced granuloma pouches and with polyarthritis indicated that the first 4 alterations originated from generalized systemic reactions to inflammation; the serum enzyme changes originated at the site of inflammation. Serums from human patients with connective tissue diseases were compared with rat serums. Alterations which were alike in rats with adjuvant arthritis and in human beings with rheumatoid arthritis were depressed albumin/globulin ratios and increased inflammation units, glycoproteins, mucoproteins, and alpha-2 globulins. Similar changes were observed in serums of rats with granuloma pouches. These biochemical changes were reflections of nonspecific inflammation and were not pathogno-monic to arthritis.