In this work the author examines the ancient sources pertaining to the apparitions of Mary on the hill called Tepeyac (near Mexico City) from December 9-12, 1531, and also the historical testimony of the event from the beginning of the sixteenth century to the present day. The author concentrates first of all on the historical dimension, in order later to manifest the theological and anthropological content of the message of Guadalupe, where Mary and the prophetic figure of Juan Diego are placed in relief. After resolving the critical problem, the apparitions are studied from a theological point of view. The fundamental value of these apparitions becomes evident when we scrutinize the popular religiosity of the Mexican people, where symbol and myth, faith and culture, are intermingled, enabling us to discover the beauty and reality of Aztec theology manifested in the language of Mary, in the flowers miraculously blooming on the hillside and in the beautiful song of the birds. The historical figure of Juan Diego, the chosen ambassador of the Blessed Virgin, has been neglected for too long. Besides bringing the reader up-to-date regarding studies, ancient and new, made about Juan Diego, the biographical material found here reveals why, when Pope John Paul II conferred the title of Blessed on Juan Diego in May 1990, he proclaimed him patron of the indigenous people of Mexico and the poor of the world everywhere. "This work is the fruit of a direct and attentive reading of the sources and a wide variety of authors. In my opinion, there is little that could be added for a pastoral knowledge of the Virgin of Guadalupe." (Gianni Colzani) Book jacket.