Summary: The kinetics of appearance of plaque‐forming and rosette‐forming cells in the spleen, blood and intestinal lymphoid tissues following single intravenous or intrajejunal injections of rats with sheep red cells have been compared. When antigen enters the body via the intestinal epithelium, local and general immune responses occur and both may contribute to antibody which appears in serum. The greatest response occurs in the mesenteric lymph nodes, and in these tissues it follows the pattern normally observed in lymphoid tissues following parenteral inoculation of antigen. Large numbers of rosette‐ forming cells appear rapidly amongst the cells of the intestinal lamina propria and submucosa; the plaque‐forming cell response is delayed by at least four days and is relatively small. It is suggested that the bulk of the latter cells are formed in other tissues and migrate to the lamina propria via the blood. The poor antibody‐forming capacity of the Peyer's patches has been demonstrated in these experiments, suggesting that these tissues may lie concerned with other immunological functions of the rat.