The objective of this case series and literature review is to characterize the clinical course and prognosis of HIV-infected patients with Kaposi's sarcoma (KS) flare during immune reconstitution inflammatory syndrome (IRIS), a heterogeneous and sometimes fatal disorder of immune perturbation after initiation of highly active antiretroviral therapy (HAART). Medical records of 9 HIV-infected patients with KS flare after virologic and immunologic response to HAART were reviewed from a single institution. An additional 10 cases were abstracted by computerized search of the medical literature. In our single institution series, mean time to onset of KS flare was 5 weeks. Pretreatment mean CD4+ count was 190 cells/mm(3) and mean HIV viral load was 153,934 copies per milliliter. During flare, mean CD4+ count was 256 cells/mm(3) and mean HIV viral load was 1156 copies per milliliter. Similar aggregate results are represented in the literature. Six fatalities are reported, 4 from pulmonary KS and 2 from unrelated causes. Systemic chemotherapy universally led to tumor regression, but was administered in only 10 of 19 cases. In no instance was HAART discontinued. Onset of IRIS-associated KS flare is observed as early as 3 weeks, with most cases diagnosed within 2 months after immunologic and virologic response to HAART. Such a flare does not necessarily portend a poor prognosis. Even for those patients with rapidly symptomatic KS, early systemic chemotherapy is effective in suppressing IRIS-associated flare. Close clinical supervision is warranted for the KS patient initiating, changing, or resuming HAART. Particular vigilance is recommended for pulmonary involvement.