Résumé : One hundred twenty-nine 111In-oxine-labeled leukocyte scintiscans have been performed in 117 patients with cancer in order to diagnose localized infectious disease. Of the 115 contributive scans, 40 were in patients with localizing signs, whereas in 75 fever of unknown origin constituted the indication for this examination. The overall specificity of the method was 95.4%, the overall sensitivity 86%, and the global accuracy 91.3%. In 10 cases with localizing signs, the 111In-oxine granulocyte scintigram allowed exclusion of the diagnosis of infection, whereas in 17 instances without localizing signs, a focal infectious process was demonstrated. Heterologous donor leukocytes were used successfully in five instances. With the exception of accumulation of label at the site of an osteolytic metastasis in one case, no uptake was observed in primary or secondary tumors. It is concluded that 111In-oxine-labeled leukocytes constitute a valuable tool in the diagnosis and localization of infection in patients with malignant disease.