Studied were the changes in the total count of the white blood cells, the leukocyte formula, and the T- and B-lymphocytes of young pigs (2-3 months old) at various intervals following treatment with an E. coli enterotoxin. It was found that there set in an essential drop of the total count of the white blood cells during the first 24 hours after treatment, with a following rising trend. There were also characteristic changes in the ratio between the various types of white blood cells, with a rise of the lymphocytes and monocytes. The level of T-POK and B-POK rose after the endotoxin was injected--for the T cells it reached peak values between the 3d and 5th day, while for the B cells it was highest between the 5th and 7th day. There was a following drop with both types of cells, and by the 15th day the initial level was reached.