Objectives: There is epidemiological evidence that reproductive factors and reproductive hormones are important in the incidence of breast cancer. Previous research has yielded consistent results on the effects of parity (previous births) and estrogen receptor (ER) status on women developing breast cancer. The aim of this study is to investigate the feasibility and utility of a larger study with North Carolina Central Cancer Registry patients to examine the association between parity and ER status among breast cancer patients. We did not examine the prognosis or survival of ER-positive versus ER-negative women. Methods: This study employed convenience sampling techniques and examined the influence of parity on ER values among 1995 North Carolina breast cancer patients. Subjects included 103 women ages 32 to 87 years, living in three different regions of the state, who received treatment in 1995 in hospitals with cancer registries. Two groups were compared for statistically significant differences. The first group consisted of breast cancer patients who had one or more full-term pregnancies; the comparison group was composed of women with breast cancer who had not carried a pregnancy to full term. Our hypothesis was that positive ER status would be higher in the group with no full-term pregnancies, since they would have had uninterrupted ovulatory cycles and therefore more estrogen stimulation of their breast tissue, potentially leading to cancer. Measuring and comparing ER status in the two groups was a preliminary approach to test this hypothesis. Results: The results suggest that, when women’s age and stage of disease are controlled, there is a link between parity and ER status among North Carolina women with breast cancer. Conclusion: We recommend another study with more subjects to further investigate the association found here between parity and ER status.