The cellular stores of iron in granulocytes and platelets isolated from 29 patients with ankylosing spondylitis were measured by the nuclear microprobe technique. The mean iron content in polymorphonuclear cells (PMNs) was 32 (SD 3) micrograms/g dry weight and in platelets 11 (2.6) micrograms/g dry weight. Corresponding values for age and sex matched healthy controls were 5.2 (1.9) and 4.6 (0.8) micrograms/g (p less than 0.001). Significant correlations were found in the patient group between (PMN) iron and the circulating levels of transferrin, total iron, and lactoferrin (p less than 0.05). PMN iron was not related to serum ferritin. Platelet iron correlated with transferrin (p less than 0.01) but not with the other iron binding proteins. Significant relationships were also found between the PMN iron stores and the inflammatory activity defined by erythrocyte sedimentation rate (ESR) and the immunoglobulins A and G. These data further illustrate the altered iron kinetics in chronic inflammatory disease and record the fact that the redistribution of iron associated with the inflammatory process also includes granulocytes and platelets.