The expression of the c-erbB-2 oncogene has been evaluated using an immunohistochemical technique with the 21N polyclonal antibody in paraffin embedded tissue from 465 patients treated between the years 1975-1981 for Stage I and II breast cancer. One hundred and four (22%) patients exhibited positive staining. This was not associated with any other variables. Expression of the oncogene was associated with significantly poorer survival which was independent of other tumour variables.