Subcutaneous trastuzumab has recently become available nationally on the Pharmaceutical Benefits Scheme for locally advanced and metastatic HER2-positive breast cancer. Its unique formulation with recombinant human hyaluronidase temporarily interrupts the extracellular matrix integrity of the body’s subcutaneous tissue, enabling painless and straightforward drug delivery. Studies suggest that the 600mg fixed dose 3-weekly, no requirement for intravenous access or loading doses, provides a convenient and timesaving alternative from the traditional weight based dosing of intravenous trastuzumab for patients and busy cancer day units alike.1,2 However, does this actually translate into a reduction in drug preparation time, patient chair time and drug wastage for the ‘real life’ Australian clinical setting? Clinical trials have demonstrated comparable pharmacokinetics, efficacy and tolerability between subcutaneous and intravenous trastuzumab.3,4 Does the one dose fits all approach with subcutaneous administration ensure long-term disease free survival rates and an adverse effect profile similar to that of intravenous trastuzumab at the extremes of population i.e. in obese or underweight patients?