Studies were conducted to compare the antibody production of the Delayed Amelanotic (DAM) line of chickens with that of the line from which it originated, the Brown line (BR), and a distantly related environmental control, the Light Brown Leghorn (LBL). Total agglutinating antibody titers following immunization with sheep red blood cells (SRBC) or Brucella abortus (BA), were determined at 4, 6, 8, 10, 12, 16, and 20 weeks. The SRBC titers of DAM line birds were significantly higher than those of LBL birds but not BR birds at young ages (4 to 8 weeks) and at 20 weeks. The BA titers of DAM and BR lines were significantly higher than those of the LBL line at 4 and 6 weeks. We conclude that the DAM line exhibits hyperreactivity in B-cell function, which may be related to the line-associated pigmentation destruction. These studies also confirm that age is an important factor in making comparisons of antibody production between different genetic stocks.