Four experiments were conducted to determine the effect of Na and Cl on the antibody response to sheep red blood cells (SRBC). In the first two experiments, Na and Cl were supplemented in the diet together as NaCl at levels from 0 to .75%. In two additional experiments, Na and Cl were supplemented independently; levels varied from .04 to .24% total dietary Na and from .07 to .36% total dietary Cl. Results of the first two experiments indicated that dietary Na and Cl levels above that found in a corn-soybean diet improved the antibody response to SRBC. Additional studies showed that the humoral immunity was significantly suppressed when chicks consumed diets with less than .14% Na and .17% Cl. Increasing dietary Cl from .17 to .27% when dietary Na was .04% suppressed the antibody response. Also, increasing dietary Cl from .21 to .36% when dietary Na was .14 or .24% suppressed the antibody response. The immunosuppression of the humoral response of chicks was determined to be not related to the decreased feed intake resulting from inadequate Na and Cl in the diet.