The major findings of a comprehensive study of the major aspects of rock cavity construction of a large nuclear power plant are: 1. Current technology is adequate for the realization of such construction. 2. A method for estimating the probability of rock fallout and gross cavity instability is presently not available. 3. Certain design modifications and amplifications must be made to prevent dependent failures. 4. No significant reduction in the immediate radiological effects of Class 9 accidents will result unless special design measures are made for this purpose. 5. The vulnerability of the plant to certain external effects is significantly reduced. 6. The total time for the realization of such construction will be significantly longer than that for a traditionally constructed plant. 7. The extra cost will be substantial.