We demonstrate the introduction of high carrier densities into two and three-dimensional magnetic semiconductor heterostructures that contain large local concentrations of magnetic moments. The use of (ZnSe)(m-f)(MnSe)(f) digital alloys readily allows the fabrication of epilayer samples of moderate Mn composition with carrier concentrations up to similar to 10(19) cm(-3). Modulation doping of ZnSe/Zn1-x-yCdyMnxSe quantum wells enables the fabrication of a 2-D electron gas confined within the magnetic region with sheet concentrations up to similar to 6 x 10(11) cm(-2). (C) 1996 American Institute of Physics.