Inflammatory lesions in 7 patients have been investigated using labelled in vivo granulocytes. Targeting of white cells was done with a monoclonal antibody, mouse IgG1 reacting with NCA (non-specific crossreacting antigen) and CEA (carcinoembryonic antigen) (BW 250/183) labelled with 99mTc. All inflammatory lesions were visualized, with excellent quality scintigram, between 3-6 and 24 h after the injection. Because the antibody can be stored in a freeze-dried form and labelled at any time with 99mTc without cell separation being necessary, the method appears to be suitable even for use in acute diagnosis.