Diamond, the best thermal conductor known, is the ultimate choice as a substrate for three dimensional (3-D) multichip modules (MCMs) in the next generation compact, high power and high speed computers. It has only recently become available as a large area free-standing substrate fabricated using various chemical vapor deposition (CVD) techniques. There are several challenges and technological hurdles which must be resolved before diamond based MCMs becomes a reality. At HiDEC, University of Arkansas, we are actively involved in 1) designing diamond substrate based MCMs, 2) synthesis of diamond thin films and substrates, 3) polishing and planarizing diamond substrates, 4) laser drilling of via holes in diamond and, 5) metallization and dielectric coatings on diamond substrates for multi-layer interconnects (MLI). This paper presents a critical review of novel technologies that have been/are being developed at HiDEC for the fabrication of diamond based MCMs.