OBJECTIVES:  To review the efficacy, safety and health care related quality of life (HRQoL) trastuzumab monotherapy in treatment of metastatic HER2+ breast cancer. METHODS:  We conducted a literature review to assess the clinical efficacy of trastuzumab monotherapy in mBC. Our review searched the MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials (CENTRAL) databases. The review included randomised-controlled trials (RCTs) and non-comparative Phase II studies. RESULTS:  The search identified 1,600 records for screening after removal of duplicates. 16 publications on 14 different studies were finally selected for inclusion. The studies were in untreated patients and/or in patients who had received previous anticancer treatments, most commonly chemotherapy. Trastuzumab was shown to have antitumour effects in terms of overall response rate (partial and complete), which ranged from 12% to 46% in identified studies. The studies reported median progression free survival between 3.7 and 22.6 months. Two studies reported data on overall survival (OS) end points. One study reported OS of 13 months with a median follow-up of 12.8 months. Another study reported that 67% patients were alive at median follow-up at 11 months. Trastuzumab used as a single agent appears to have a low toxicity level. The most common adverse events tended to be infusion related (fever and chills). The most clinically significant adverse event was cardiac toxicity. There were limited comparative analyses available for trastuzumab monotherapy, which means that there is uncertainty about the effectiveness of trastuzumab monotherapy. The HRQoL reported in publications demonstrated that trastuzumab monotherapy may be associated with not only a lack of deterioration of HRQoL but also with a positive effect on HRQoL in patients with MBC. CONCLUSIONS:  In addition to improving clinical outcomes, trastuzumab monotherapy has a stabilising or positive effect on HRQOL in patients with HER2-postivity metastatic breast cancer, particularly those with responsive disease.