SummarySera of rabbits immunized with pooled rabbit submaxillary gland suspensions were studied by complement fixation and tanned cell hemagglutination technics. 1. Some of these antisera (3 out of 7) fixed complement in presence of rabbit submaxillary gland extracts. 2. Complement fixing activity of 2 of the 3 sera studied in detail was specific for submaxillary gland extracts within the limits of antigens tested. One of 3 serologically active sera (#1565) cross reacted with parotid gland extracts. 3. The globulin fraction of submaxillary gland extracts contained virtually all the material in the extract which was reactive with rabbit submaxillary gland antibodies. Some activity was also found in the microsome fraction. 4. Extracts of the submaxillary glands of the antibody-producing animals themselves reacted just as strongly as those of other rabbits, indicating the autoantibody nature of the antibodies elicited by isoimmunization. 5. Most of the rabbit antisera (6 out of 7) agglutinated tanned red cel...