This volume contains written versions of the papers presented at the Third Inter national Conference on Amorphous and Crystalline Silicon Carbide and Other Group IV-IV Materials (lCACSC 90), which was held at Howard University, April 11-13, 1990 in Washington, DC. The ICACSC continued to provide an international forum for discussion and exchange of ideas regarding the current state of research aimed at developing silicon carbide devices and circuits and related materials. ICACSC attracted over one hundred participants from seven countries. A special session was held in honor of the eight Soviet scientists who attended the conference. The substantial increase in the number of papers compared with the previous year is an indication of the growing interest in this field. The conference also included a poster session for the first time. This volume contains 54 refereed contributions grouped into four parts. Several exciting new results are reported for the first time here: SiC-based solid-solution growth and technology, the formation of SiGe heterostructures by ion implantation, 6H-SiC substrates grown by the sublimation method, expla nation of the appearance of negative differential resistance in a N+PN-SiC-6H transistor by the Wannier-Starck effect, the formation of amorphous SiC/Si het erojunctions by the polymer route, and the prospects of developing SiC bipolar transistors and thyristors.