Between seven and 21% of patients treated with the specific tyrosine kinase inhibitor STI571 have been reported to develop mild-to-moderate severity of adverse cutaneous reactions. We report a patient in the blast crisis phase of chronic myeloid leukaemia who developed a life-threatening cutaneous reaction, Stevens-Johnson syndrome, following 1 week of STI571 therapy. This report may serve to remind the clinician about the possible severe cutaneous side-effects of STI571 before instituting more extensive clinical application of this agent in the future.