Originally, Mark Lehner traveled to Egypt as a tourist in 1972. However, he was at that time a devotee of the ideas of Edgar Cayce (the Sleeping Profit) who is will known by ancient Egypt enthusiasts. Edgar Cayce was a mystic who believed that the civilization of Atlantis had entrusted their knowledge and technology to the ancient Egyptians. In fact, Cayce believed that he had lived in ancient Egypt under the name Ra-Ta. He might be considered one of the founders of modern "alternative though" on matters of Egyptian antiquity. For example, it was he who believed that there was an Atlantian "Hall of Records" buried beneath the right paw of the famed Sphinx, a theory that sometimes surfaces amongst the fringe elements of ancient Egyptian enthusiasts even today. In his youth, Mark Lehner traveled to Egypt in order to further that claim, as well as other visions of Edgar Cayce. He even published at least one book in support of Edgar Cayce's claims (The Egyptian Heritage, 1974). It is perhaps interesting that fringe elements continue today to reference this early work of Dr. Lehner, because long ago he became a convert to more traditional Egyptology.

Perhaps one of the most famous living experts on the study of the pyramids at Giza today is Mark Lehner. Lehner has devoted twenty-nine years of study and research to the pyramids, first enrolling at the American University in Cairo in 1973 under a grant from the Edgar Cayce Foundation. Lehner speculated that the people of the lost civilization of Atlantis had entrusted their knowledge and technology to the people of Egypt before their civilization was destroyed. Supposedly the blueprints for the construction of the Great Pyramid at Giza was located in a "Hall of Records" under the right paw of the famed Sphinx. When the theory turned out to have no basis in reality, Lehner still carried with him a fascination with the Sphinx and the pyramids, especially with how they were actually created.

From 1979 to 1983, Lehner directed projects on the Sphinx and the Isis Temple, and since then, has directed what is known as the Giza Plateau Mapping Project. This project includes mapping the area of the Giza Plateau where the pyramids are found, excavating sites of interest within that area, and publicizing his findings. Lehner worked in the tomb of the Pharaoh Khufu, Khufu's mother (the Queen Mother), the Wall of the Crow, which is thought to be some sort of a gateway to the pyramids of Giza, and more recently has begun excavating a village at Giza thought to have housed the pyramid workers. It is estimated to be about 4,500 years old and could have housed as many as 20,000 workers.

In 1990 he received his Ph.D in Egyptology from Yale University studying under Williams Kelly Simpson. He was Assistant Professor of Egyptian Archaeology at the University of Chicago from 1990 until 1996. Today, he remains a research associate of both the Oriental Institute of the University of Chicago, as well as of the Semitic Museum at Harvard University.

Since it founding in 1985, Mark Lehner has been the president of Ancient Egypt Research Associates (A.E.R.A.), which was established for the purpose of funding and facilitating the research of the Giza Plateau Mapping Project From 1988 until present he has been the Director of the Giza Plateau Mapping Project excavations south of the Great Sphinx. At first this work was under the auspices of Yale University and the American Research Center in Egypt. From 1990, the work continued under the banner of the Oriental Institute of the University of Chicago, and since 1994, the Harvard Semitic Museum has been a cosponsor.

This work is uncovering the remains of a royal urban production center. An area of three hectares has been exposed. Dating from the time the Giza Pyramids were under construction 4,500 years ago, this orthogonally planned settlement includes one of the oldest known paved streets, Egypt's oldest known hypostyle hall, and oldest copper working facility.

However, Mark Lehner probably, at least in the public eye, remains most notable for his work with the great pyramids. He is often called upon by media outlets such as the Discovery Channel, PBS (NOVA), the National Geographic Society and the BBC for his vast knowledge of pyramids and the Giza Plateau in general. One of his projects, in which he and others built a small pyramid using ancient techniques, has shown that the Great Pyramid may not have required either the time span, nor the vast number of laborers to traditionally thought for its completion.

Today, Mark Lehner is considered to be a pioneer in the use of state-of-the-art computer graphics and remote sensing technology to model the ancient configuration of the Giza Plateau. He remains a Research Associate and Visiting Assistant Professor of Egyptian Archaology at the Oriental Institute and the Harvard Semitic Museum.

His publications include The Complete Pyramids: Solving the Ancient Mysteries, published in 1997, hosting several NOVA productions on the pyramids and a special on FOX television in which he, along with colleague Zahi Hawass will lead a camera crew for a first-time look inside the complex burial shafts of the Queen Mother, at Khufu's Great Pyramid at Giza. The special airs live September 16, 2002.