Genetic polymorphism of properdin factor B (BF) was investigated in sera from 259 healthy individuals living in Guangzhou, southern China, by means of high voltage agarose gel electrophoresis followed by immunofixation. Besides the common phenotypes, SS, FS, FF and SS07, two rare heterozygous phenotypes tentatively named as SSG1 and SFG2 were observed. The allele frequencies estimated for BF*S, BF~'F, BF*S07, BF*SG1 and BF*FG2 were 0.8668, 0.1197, 0.0077, 0.0019 and 0.0039, respectively. Family data indicated an autosomal, codominant inheritance for the BF*FG2 allele.