CD45 is expressed on all B cells and has been reported to be essential for their B cell receptor mediated stimulation. The present study addressed T-cell-independent B cell responses in CD45-deficient mice using the glycoprotein (G) of vesicular stomatitis virus (VSV) as a model antigen. VSV-G exists in two forms exhibiting different degrees of repetitiveness. In mice, the two forms of VSV-G induce either a type 1 or a type 2 T-cell-independent B cell response. We found that CD45-deficient mice mounted T-cell-independent B cell responses to both forms of VSV-G. This demonstrates that the B cell receptor complex is able to generate a functional signal in the absence of CD45, provided the cross-linking stimulus is sufficiently strong.