DXM application in dogs in an amount of 0.3 or 0.6 mg/kg b.w. results in a very transient increase of CFU-C within 1 h after administration and a subsequent progressive decrease of circulating CFU-C reaching a nadir at about 7 h. The pattern seen in the blood CFU-C concentration matches the pattern of change seen in the total lymphocyte population. The CFU-C changes observed do not correspond to the change of the PMN number in the peripheral blood after DXM. There is a 3 fold increase in the number of circulating PMNs. The data suggest that the blood CFU-C follow in principle the pattern of the other mononuclear cells, usually described as lymphocytes. The pattern of change of CFU-C and lymphocytes however must not be interpreted to mean that the pathophysiological mechanisms behind this changes are the same considering the CFU-C population and the other lymphocyte populations.