Two polymorphisms of human complement C7 (IEF and M/N) have been studied in the Han population from Chengdu, People's Republic of China. One was determined by polyacrylamide gel isoelectric focusing (IEF) of neuraminidase-treated EDTA plasma, whereas the other was performed by a combination of two ELISAs using a C7-allospecific monoclonal antibody or polyclonal C7-specific IgG as coating antibodies. In 121 Chinese subjects IEF patterns of C7 were classified into three common and four rare phenotypes. The C7 IEF allele frequency estimates for C7*1, C7*2, C7*3, C7*4 and C7*7 were 0.831, 0.095, 0.045, 0.025 and 0.004, respectively. The C7 M/N typing in 113 Chinese individuals revealed the following allele frequencies: C7*M = 0.805, C7*N = 0.195. Allelic associations between C7 IEF alleles and the C7 M/N alleles are also discussed.