AbstractCirculating immune complex (CIC) in patients with hepatitis B virus associated glomerulonephropathy was fractionated into two parts by sucrose gradient ultracentrifugation. A CIC of higher molecular weight (more than 900,000 daltons) consisted of hepatitis B virus surface antigen (HBsAg), and one of lower molecular weight (between 900,000 and 66,000 daltons) consisted of hepatitis B virus e antigen (HBeAg). The patients with membranous glomerulonephropathy (MGN) had much more CIC of higher than of lower molecular weight, while deposits in the glomerular basement membrane were stained with anti‐HBeAg but not with anti‐HBsAg. A patient with minimal changes had only higher molecular weight CIC and no deposits in the kidney. Our results suggest that lower molecular weight CIC containing HBeAg may play an important role in the development of MGN.