[Four stages in the history of the Centro Médico Nacional Siglo XXI of the IMSS].

This document presents four stages in the history of the Centro Médico Nacional Siglo XXI (Centro Médico Nacional XXI Century) of the Instituto Mexicano del Seguro Social. The first stage started at the end of the third decade of the twentieth century and ended in 1961, it corresponded to the conception, planning and construction of what was to be the Centro Médico del Distrito Federal (Centro Médico of the Distrito Federal) belonging to the Secretaría de Salubridad y Asistencia (Ministry of Health and Assistance). The second stage began when the Center was acquired by the Institute, then was known like Centro Médico Nacional (Centro Médico Nacional ), being put into full operation in 1963, more than twenty-two years later, in 1985, an earthquake virtually ended it, immediately began its reconstruction, finishing the second stage. In 1989 began the third stage, different and new buildings complemented or replaced the structures damaged or destroyed by the earthquake which formed the now Centro Médico Nacional Siglo XXI (Centro Médico Nacional XXI Century). In 2004 the fourth stage opened when the four hospitals of the Center were categorized like Unidades Médicas de Alta Especialidad (High Specialized Medical Units).