Immunotherapy targeted against microbial toxins and host mediators has been studied in many preclinical investigations and clinical trials of sepsis during the past 20 y. Intravenous immunoglobulin, including both monoclonal and polyclonal antibodies, represents one such immunotherapeutic strategy. Mononclonal antibodies directed against endotoxin or tumour necrosis factor-alpha have been tested extensively in clinical trials, but have so far failed to reveal a significant effect on mortality rates. Several studies have assessed the efficacy of polyclonal intravenous immunoglobulin (IVIG) in sepsis, with varying results. Although there are no conclusive data available to date to support the use of IVIG therapy in all sepsis cases, there are strong indications that certain defined septic subgroups, such as streptococcal toxic shock syndrome caused by group A streptococcus, will benefit from its use. This review briefly summarizes the clinical trials on IVIG therapy in sepsis, and describes in more detail the mechanistic actions of IVIG and the clinical data that support the use of IVIG as adjunctive therapy in severe invasive group A streptococcal infections.