Preferential use of particular VH gene families in the response to specific antigens has been demonstrated in several systems. The lack of responses to certain types of antigens, therefore, could be the result of deletion of or failure to express some VH genes. Because CBA/N mice, which carry the X-linked immunodeficiency (xid) gene defect, have been shown to be unresponsive to thymus-independent polysaccharide antigens, it was of interest to examine if this unresponsiveness could be accounted for by abnormal expression of particular VH gene families. Using in situ hybridization on B cell colonies, we determined the expression of nine VH gene families in CBA/CaHN females (genotypically normal), CBA/N males (xid) and females (xid), and (CBA/N x CBA/CaHN)F1 males (xid) and females (phenotypically normal). Our results indicate that VH gene family expression, including the S107 family, in CBA/N males and F1 males, is similar to that of CBA/CaHN and F1 females with predominant expression of J558, the largest gene family, in all individuals. Interestingly, CBA/N female mice, which carry two defective X chromosomes, as a group expressed significantly reduced levels of the J558 gene family, and as individuals showed variation in which family was predominantly expressed. We conclude that the unresponsiveness of mice with the xid defect to polysaccharide antigens can not attributed to a failure to express the nine VH gene families that we examined. Our findings do not support previous studies (Primi, D., and P.-A. Cazenave 1986. J. Exp. Med. 165:357), which found an absence of expression of the S107 family in xid mice.