Digital materials such as the ones shown by Objet’s Connex family demonstrate that a new material with desired characteristics can be achieved by combining two different base materials with various concentrations and structures. We investigate the feasibility of using additive manufacturing processes based on digital mask projection in the fabrication of such digital materials. A multi-material mask-image-projection-based Stereolithography process has been developed. The related challenges on the development of such a process are identified. Our approaches to address such challenges are presented. A testbed has been developed to fabricate component with designed digital materials. Experimental results illustrate desired material properties can be achieved based on the developed process. Several multi-material designs have been produced to highlight the capability of this promising technology for fabricating three-dimensional, multi-material objects with spatial control over placement of both material and structure. The limitations and challenges for future development have also been identified.