Imatinib mesylate (Gleevec) is widely-used in the treatment of chronic myeloid leukaemia (CML) and gastrointestinal stromal tumour. Up to four percent of patients treated with imatinib may develop hepatotoxicity, which usually resolves with discontinuation of the drug. We report a 45-year-old Chinese man with CML and chronic hepatitis B virus infection, on imatinib treatment, presenting with herpetic rash and acute liver failure. This case illustrates the diagnostic challenges in the management of such a patient, as well as the need for greater vigilance in the monitoring of liver function tests for patients treated with imatinib. A short review on imatinib-related hepatotoxicity is also presented.