The combination of exemestane and everolimus is a new treatment option for metastatic hormone-sensitive breast cancer. This treatment is used after progression on non-steroidal aromatase inhibitors. The treatment is generally well tolerated, but sometimes leads to minor or even serious side effects. It is important to be aware of these side effects and to treat them. We describe two patients who had to cope with various forms of toxicity: a 73-year-old woman with aphthous mouth lesions and a 49-year-old woman with pneumonitis. We then discuss the efficacy of the combination exemestane and everolimus and its positioning in the treatment of metastatic hormone-sensitive breast cancer. Finally, some common and some potentially serious side effects will be discussed, along with recommendations for their management and indications for distinguishing side effects from disease progression.