The purpose of this paper is that of analyzing the hypothesis that, as originally stated by its creators, the reengineering methodology for the improvement of efficiency and productivity, cannot be successfully implemented in Spanish public hospitals, and in fact, the so called experiences do not keep with the basics of such an approach. The technique employed for this study consisted, on one hand, of reviewing and comparing the literature published on this subject and, on the other, on experimentation by means of a case study conducted at a public hospital for the purpose of testing out the outlined hypothesis. The review and comparison of works previously published on this subject revealed that the technique for improving on-the-job efficiency according to the theory-based concepts of the process reengineering approach is not adaptable to public hospitals in Spain. The case study supported this finding, additionally highlighting the fact that in order for any relatively major changes in the working processes at public hospitals to be recommended, a number of organizational and human factors must be taken into consideration as aspects involved regardless of the methodological approach taken. The indiscriminate implementation in public hospital administration of trends currently fashionable in the business administration field may defeat its own purpose if these trends are not previously evaluated prior to being implemented. An assessment must first be made as to their being suited to the intended purpose.