Cyclophosphamide induced pneumonitis is a rare adverse event in patients receiving adjuvant chemotherapy for breast cancer. It has been infrequently reported in the literature and based on the described cases it appears to be associated with dose dense regimens. We report three cases of cyclophosphamide induced pneumonitis who were treated at our centre. Our cases illustrate that careful attention must be paid to timing of symptoms to ensure the correct causative chemotherapy agent is identified so that potentially curative agents in the chemotherapy regime are not omitted.