Since its first use in 1952, human immunoglobulin has been used to treat people who have inherited antibody deficiencies. This article summarizes IVIG clinical development in primary immunodeficient patients and manufacturing improvements introduced over time. Manufacturing improvements include purification procedures that have reduced the incidence of adverse events and improved clinical efficacy, as well as virus inactivation and removal steps that have increased safety from blood-borne infections. Current manufacturing procedures, IVIG production trends, and recent clinical trial results are also reviewed.