Lapatinib is an oral receptor tyrosine kinase inhibitor, inhibiting both the ErbB-1 and ErbB-2 receptors. Lapatinib has been shown to have activity in ErbB-2-overexpressing breast cancer in several phase II and III clinical trials. Specifically, lapatinib is effective in patients with metastatic breast cancer, with inflammatory breast cancer, and possibly, with brain metastases. An ongoing clinical trial and another anticipated clinical trial will investigate lapatinib as adjuvant treatment in early-stage disease. Lapatinib has specific toxicities, the most common being diarrhea and rash. Cardiac toxicity is rarely seen with lapatinib. This paper reviews lapatinib-associated toxicities and provides practical management recommendations based on available data.