OBJECTIVES: evaluate the relationship between the non compliance to the claim of medication and incidence of hospitalization in patients with breast cancer in oral antineoplastic therapy. METHODS: case-control study in patients with breast cancer, that claimed their medicines in pharmacies between january of 2012 and December 2014. Was defined as a case patients that during the observation period claimed their drugs in pharmacy <95% of the time. The sample size was calculated for a proportion of cases exposed 40% an OR of 3.7, a relation case-control 1:2, a 95% confidence and an potency 80%. The final sample was composed of 40 cases and 80 controls (randomly selected from the same cases population). For univariate analysis was used absolute and relative frequencies and summary measures. For binary analysis contingency tables, chi-square tests. The statistical measure of force used was the Odds Ratio. RESULTS: the proportion of hospitalized patients who did not comply with the claim of medicines in pharmacy was 45.7% (p:0.06). The non adherent patients were hospitalized 2.14 times more than compliant patients, (OR 2.14 [IC95% 0.94-4.8]). If we avoided the non compliance claim of medications in pharmacies, we would avoid 24% of hospitalizations (FA 24% [IC95% 5.4%-5.7%]). CONCLUSIONS: the non compliance to claim medication in pharmacy is a influence factor increased in the incidence of hospitalization in breast cáncer patients.