Epidemiological evidence suggests that exposure to the pesticide dieldrin, is associated with increased risk of breast cancer and mortality. We hypothesize that dieldrin promotes breast cancer by increasing survival of breast cancer cells. The aims of this study were to measure the effect of dieldrin on survival of breast cancer cells and the expression of tyrosine kinase B (TrkB), a suppressor of anoikis (apoptosis triggered by inappropriate anchorage). The human breast cancer cell line MDA-MB-231 was treated with dieldrin and proliferation, viability and resistance to anoikis were measured. TrkB expression was measured by Western blot in lysates and by immunohistochemistry in human tissue specimens. Dieldrin increased resistance to anoikis and TrkB expression. TrkB was expressed in a subset of high-grade breast carcinoma specimens. Our results demonstrate that dieldrin increases resistance to anoikis and expression of TrkB and show for the first time TrkB protein expression in human breast cancer.