Monocytes infiltrate glomeruli during mesangial deposition of ferritin, and during experimental glomerulonephritis. To determine whether this is solely a local phenomenon, leucocyte infiltration in other organs has been studied following intravenous ferritin injection. Lewis rats received an i.v. injection of 150 mg ferritin/100 g body weight. At 24 h there was a peripheral blood leucocytosis (ferritin-treated rats 26.32 +/- 13.7, control rats 8.54 +/- 2.41 X 10(6) cells/ml) due to increase in polymorphs and monocytes. Bone marrow cell counts fell (ferritin-treated rats 49 +/- 7, control 80 +/- 11 X 10(6)/100 g body weight). Cell counts on cell suspensions of perfused, enzyme-digested lung, liver and spleen, and lung lavage showed major significant increases in total cell counts: lung 250 +/- 36 (89 +/- 16), lung lavage 2.6 +/- 0.8 (1.4 +/- 0.5), liver 140 +/- 37 (60 +/- 11), spleen 306 +/- 38 (200 +/- 27) X 10(6)/100 g body weight (control values in parentheses). Cytospin preparations of these suspensions, stained for non-specific esterase showed that the increase in cell numbers was due to increases in non-specific esterase-positive cells (monocytes) and polymorphs. These results demonstrate a generalized leucocyte mobilization, sequestration, and tissue infiltration after i.v. ferritin. The renal glomerulus therefore is not the only site of leucocyte accumulation. These findings may have relevance for studies on inflammation mediated by leucocytes in models of experimental immune complex glomerulonephritis.