Abstract: Improved nucleus pulposus implants are provided to better accommodate the disc nucleus space, to provide a modified compressive modulus, to facilitate positioning, to enhance fixation, and to facilitate effective implantation and use. Some implants have sloped upper and/or lower surfaces to provide a “wedge-shaped” implant, while other implants have circumferential grooves, and/or have radiographic markers, and/or are modified by including a material having a compression profile that differs from the compression profile of the predominant material of the implant. Some implants have surface features to enhance fixation to surrounding surfaces.