This study compares the cell labelling characteristics of two 111In-oxinate formulations. The two preparations differ by the solubilizing agent of the chelate and the total amount of oxine. White blood cell suspensions were obtained by standard separation techniques and were labelled with either of these formulations. The labelling efficiency was higher for 111In-oxinate in aqueous solution (compound B) compared to the preparation where an organic solubilizer was added (compound A) (79.2 +/- 7.7 vs 68.6 +/- 17.6%, respectively, P = 0.03). Red blood cells contaminating the cell suspensions incorporated a higher fraction of 111In if the cells were incubated with the aqueous 111In-oxinate preparation (22.6 +/- 4.6 vs 4.8 +/- 4.6%, respectively, P less than 0.0001). The uptake of activity by polymorphonuclear cells was reduced with compound B (46.1 +/- 12.8 vs 63.8 +/- 15.8%, respectively, P = 0.0002) whereas the fraction retained by mononuclear cells and platelets was similar (31.3 +/- 13.9 vs 31.4 +/- 15.0%, respectively). The recovery from the vial was higher for 111In-oxinate in an organic solution (86.6 +/- 1.82 vs 60.3 +/- 14.3%, respectively, P less than 0.0001). Twenty four hours after administration of the labelled cells, the vascular compartment was less frequently visualized if cells were labelled with compound A (8% of the scintigrams vs 62.5% respectively, P less than 0.0001). High quality images were more often recorded after the administration of cells labelled with compound A (60.0% of the images vs 23.5%, respectively, P less than 0.02). The image quality of scintigrams was not related to any of the other cell labelling parameters.(ABSTRACT TRUNCATED AT 250 WORDS)