Mice were injected intraperitoneally with Sepharose 4B beads coupled with hapten NIP, and their anti-NIP response was studied by counting antibody forming cells and determining serum titers. Mice responded well to doses of 0.7 ml of packed beads but 0.3 and 1.2 doses induced much weaker responses. Anti-NIP titers in recipients of 0.7 ml of the antigen lasted nearly constant for at least 7 weeks. Both T cell status of the recipient and use of adjuvant had an effect on the response. Antigen without adjuvant induced primarily IgM antibodies in normal mice, but IgM and IgG in nude mice. When Hemophilus pertussis or polyacrylic acid was used as adjuvant both normal and nude mice produced IgM and IgG antibodies, and normal mice produced in addittion IgA antibodies.