White blood cell counts and circulating interleukin-6 concentrations were measured in male colorectal cancer patients with (n = 12) and without (n = 15) evidence of an acute phase protein response. In the group with an acute phase protein response circulating neutrophils were increased whereas serum interleukin-6 concentrations were not. These results suggest that in colorectal cancer patients although an acute phase protein response is associated with neutrophilia, both events can occur independent of circulating interleukin-6 concentrations.