Background: Kaposi's sarcoma (KS) continues to be the most common human immunodeficiency virus (HIV)-associated neoplasm with considerable morbidity and mortality. While lesions normally resolve upon initiation of antiretroviral therapy (ART), recrudescence or unmasking of KS lesions may occur as part of immune reconstitution inflammatory syndrome (IRIS). Treatment of unmasking KS-IRIS is not yet standardised. Objectives: To report the successful treatment of a patient with fulminating mucocutaneous unmasking KS-IRIS by maintaining ART and using pegylated liposomal doxorubicin (PLD). Study design: The patient, a 39-year-old HIV-positive male with no previous history of KS presented with a 2-week history of cutaneous and oral KS lesions that had disseminated rapidly over the preceding 4 days. The KS lesions appeared 8 weeks after recommencing ART. At the time of this presentation, his CD4+ count was 742 cells/mm3 with a HIV viral load <400 copies/ml. ART was maintained and treatment with PLD commenced. Results: Despite the rapid dissemination of KS lesions, virus was undetectable in plasma. In a late-stage vasoformative lesion, immunohistochemistry (IHC) for human herpesvirus 8 (HHV-8) antigen was light and diffuse, with stippled deposits within endothelial cell nuclei. Virus extracted from the lesion was HHV-8 subtype A. The patient responded well to PLD, relapsed a year later, but after further PLD, has remained well for the following 5 years. Conclusion: Despite the absence of HHV-8 viraemia, this is clearly a case of unmasking KS-IRIS. It demonstrates that this entity can be successfully treated by maintaining ART and administering PLD.