Varicella zoster virus (VZV) infection is uncommon in patients with gastrointestinal stromal tumour (GIST) and who have not been exposed to extensive radiotherapy and/or high-dose chemotherapy. We report a 56-year-old Nigerian man with GIST who developed VZV infection while on imatinib mesylate therapy. From August 2003 to November 2005, 64 patients (GIST/CML = 6/58) were enrolled into an ongoing Glivec (imatinib mesylate) international patient-assistance programme therapy for Philadelphia/bcr-abl-positive chronic myeloid leukaemia (CML) and CD117-positive GIST patients at Obafemi Awolowo University Teaching Hospitals Complex, Ile-Ife, Nigeria. The patient developed herpes zoster (HZ) infection 23 months into therapy with Glivec. With his absolute lymphocyte count at 2,774 cells per microlitre and CD4 count at 950 cells per microlitre, no obvious immunological defect was observed. Prompt resolution of symptoms without sequelae was achieved by treating with acyclovir, analgesic and dressing of lesions with desiccant. To our knowledge, this is the first reported case of HZ infection in a patient with GIST on Glivec therapy, and the response is similar to that of CML patients who developed VZV while on similar therapy.