1977年Rizzetto等首次报告在慢性HBsAg携带者的肝细胞核与血清中发现了一种新的抗原。已知乙型肝炎病毒(HBV)有表面抗原(HBsAg)、e抗原(HBeAg)和核心抗原(HBcAg),因而认为新发现的抗原是HBV的第4种抗原,当时按希腊字母顺序命名为δ抗原(delta antigen)。但现在普遍认为δ抗原并非HBV本身的组成部分,而是另一种可传染的肝炎因子,称为δ因子(delta agent)。本文就近年对δ因子的特性、检测方法和感染的临床表现等问题作一综述。生物特性与动物实验感染者血清中的δ因子被HBsAg包裹, In 1977, Rizzetto et al. First reported a new antigen found in the liver nuclei and serum of chronic HBsAg carriers. Hepatitis B virus (HBV) is known to have surface antigen (HBsAg), e antigen (HBeAg) and core antigen (HBcAg), so that the newly discovered antigen is the fourth antigen of HBV, then in Greek alphabetical order δ Antigen (delta antigen). However, it is now widely accepted that δ antigen is not part of HBV itself, but rather another infectious hepatitis molecule called delta-factor. In this paper, in recent years, the characteristics of δ-factor, detection methods and clinical manifestations of infection and other issues are reviewed. Biological characteristics and animal experiments in infected sera δ factor is HBsAg package,