Background: Adjuvant hormone therapy (HRx) improves outcomes for women with hormone receptor positive (HR+) early stage breast cancer (EBC). We evaluated predictors of appropriate use of adjuvant HRx among Medicaid enrolled women with EBC. Methods: Using linked records from the New York (NY) State Cancer Registry, Medicaid and Medicare, we evaluated the frequency and predictors of HRx use among women 21-64 years old diagnosed in 2004-6 with stage I-III HR+ EBC. HRx was considered present if there was at least one prescription for tamoxifen, letrozole, exemestane, or anastrozole during the year after diagnosis. Multivariable (MV) regression models were constructed to identify factors associated with appropriate HRx. Results: Within 1 year of diagnosis, 1049/1538 = 68% of EBC patients received HRx. Factors associated with receipt of HRx included: receipt of cash assistance (a marker of lower income), earlier stage disease, dual expression of ER+ and PR+, mastectomy and receipt of radiation therapy. Notably, comorbid medical conditions, psychosis, depression, substance abuse, race/ethnicity and age were not associated with HRx. Within 18 months of diagnosis, the proportion of women with HRx increased to 80%. Conclusions: There appears to be underuse of HRx among women with HR+ EBC enrolled in the NY state Medicaid program. Some women never receive treatment and others appear to start after considerable delay suggesting opportunities for improving EBC treatment for program participants.