BCMA (TNFRSF17), along with TACI, has recently been demonstrated to be a receptor for BLyS (TNFSF13B). Recent studies indicated substantial role of BLyS signaling pathway for systemic lupus erythematosus (SLE). In the present study, we made an attempt to screen for polymorphisms of human BCMA, and to test their possible association with SLE and rheumatoid arthritis (RA). Two single nucleotide polymorphisms (SNPs) were detected within the coding sequence, both of which were synonymous substitutions. In addition, two SNPs within the promoter, two SNPs in the 5'-untranslated region (UTR), one SNP and one single nucleotide deletion in the 3'UTR and four rare variations were detected. From the combination of the polymorphisms, it was elucidated that four major haplotypes account for most of the genotypes in the Japanese population. Association with SLE and RA was not detected, although a slight tendency for the increase of BCMA.03 in SLE was observed (P = 0.089). These results indicated that human BCMA is conserved with respect to the amino acid sequence, and evidence for association with SLE and RA was not observed.