HER2-positive breast cancer, accounting for 15 % of the total breast cancer patient population, carries in itself a bad prognosis, which has now become much better after the advent of anti-HER2 drugs. HER2-targeted therapy has significantly improved disease free- and overall survival in HER2-positive breast cancer, and has rendered better disease control both in the early and advanced disease setting. Trastuzumab treatment duration is often prolonged and poses significant time and resource challenges both on the treatment institutions and on the patient. The recent development of a subcutaneous formulation has meant a significant advance in this respect. We review the drug development of the compound and the current evidence on its use.