The objective of this study was to evaluate the efficacy and tolerability profile of sequential trastuzumab in the adjuvant treatment of non-metastatic breast cancer. We analyzed 94 patients with non-metastatic breast cancer who underwent postoperative treatment between November 2003 and December 2008 at the University of florence. All patients received one year of sequential trastuzumab after adjuvant chemotherapy. Cardiac monitoring in our study consisted of assessment of left ventricular ejection fraction (lVef) by echocardiography at baseline, after the completion of chemotherapy, then every 3 months during trastuzumab treatment and every 6 months thereafter. 91.6% of patients were alive without evidence of distant or local relapse, while 8.4% developed disease recurrence. The cumulative incidence of cardiotoxicity was 14.5%. In our experience trastuzumab given postoperatively with adjuvant chemotherapy was well tolerated and produced optimal clinical results in terms of disease-free survival.