A recombinant chimeric, mouse-human monoclonal antibody IgG1, directed against the epidermal growth factor receptor (EGFR) and labeled with the radioisotope indium-111, with potential radioimaging activity. Indium 111 chimeric monoclonal antibody 806 binds to a specific epitope on EGFR-expressing tumor cells, allowing imaging of EGFR-expressing tumor cells using gamma scintigraphy. EGFR is a receptor tyrosine kinase that is involved in the regulation of cell growth and is found to be overexpressed on the cell surfaces of many tumor cell types.