We have studied the restriction fragment length polymorphism (RFLP) of the major histocompatibility complex (MHC) class II DQ, DR pattern of a Chinese family with IgA nephropathy (IgAN). The three affected and one apparently unaffected sibling shared the same DR and DQ pattern. The subjects were homozygous for DRw12, DQw7, DQ alpha 1b. The DQw7 allele was further confirmed by polymerase chain reaction (PCR) and allele-specific oligonucleotide (ASO) probing. This study confirms that IgAN can run in a family and is consistent with the possible immunopathogenetic effects of MHC class II antigens on IgAN.