AlxGa1-xAs co-doped with Si and B was investigated to determine the effect of B on the properties of DX centers. We found the deep level transient spectroscopy (DLTS) peak of the DX center to be unchanged and also observed large persistent photoconductivity (PPC), in samples containing boron in concentrations up to 6 X 10(18) cm-3. Our finding that B has no significant effect on DX centers differs from an earlier report that the presence of low concentrations of B modified the DLTS spectrum of Si-doped GaAs under hydrostatic pressure.