The authors studied 30 consecutive archival cases of pure breast carcinoma in situ (CIS) for estrogen receptor (ER), progesterone receptor (PR), and c-erbB-2 oncogene product. Clinical factors of age and menstrual status and histologic features of tumor type and nuclear grade were determined. Some 77% represented ductal CIS, with 10% noninvasive papillary, and 13% lobular CIS. A total of 22 of 30 (73%) were ER+ and 19 (63%) were PR+; 24 (80%) were c-erbB-2+ with 11 (37%) showing strong staining; 75% of the ER-PR group had tumors of NG 3, versus 14% for the ER+PR+ plus ER+PR- groups. Nonstatistically significant trends correlating the strongly positive oncogene group with PM status, receptor negativity, and high nuclear grade were noted. The overall rate of receptor positivity, as well as the correlation with nuclear grade, is similar to that in invasive carcinomas c-erbB-2 protein expression shows a higher rate in in situ than is reported for invasive tumors, and shows a tendency to be expressed more strongly in tumors with other features of poor prognosis. Therefore, these factors may also have prognostic significance in CIS. Continued followup of this population to recurrence may provide further insight.