Beginning from the 4th Century AD, numerous great ecclesiastical complexes were constructed in the area of the late Roman Empire. Apart from the main churches, these complexes usually incorporated several other buildings either of sacred or secular purpose. The approach to these areas was in many cases emphasized by elaborated gateways. Several of these gateways are known from written sources or due to archeological excavations. The few surviving examples have, if ever, only been subject to isolated studies of single buildings. Early christian gateways have so far neither been recognized as an own type of building, nor have they been examined as a group regarding their form and function. Subject of this study is the comparative analysis of this group. The aim is a comprehensive depiction of this building type regarding its origin, form, use and evolution during the late antiquity and early middle ages. The analysis of the earliest written sources mentioning gatehouses of late antique church complexes shows a close relationship between these and the building type of pagan temple- propylea. Known examples of early christian gatehouses cover a wide range from direct reuse of antique propylea for church complexes to rebuilding and the construction of completely new structures. Spreadimg from the hellenistic- influenced eastern mediterranean area the building type can be found in Rome itself and later in the whole area of the late roman empire. As an architectural model provincial roman forms of the 2nd and 3rd century AD can be identified rather than classic and hellenistic ones. Representative gateways can be found only in the most elaborated church complexes. They were constructed either on sights of special religious importance, such as a tombs of Apostles, or as a demonstration of (in most cases imperial) power. In the city of Rome the developement of the building type can be retraced during the whole period from the 4th to the 9th century AD. The great ecclesiastical complexes of the city, especially old St. Peter, were serving as an example for church buildings all over europe. By the end of the 4th century AD, the approach to old St. Peter replaced the via sacra towards the temple of Jupiter Optimus Maximus as a ceremonial location for processions. As a consquence it was emphasized by several triumphal arches. This principle was taken over by numerous church complexes, namely by those which were important destinations for pilgrims. The monuments that accentuated the pilgrim‘s approach incorporated architctural elements of both triumphal arches and gateways. The late 6th century marks a break in the developement of the building type. For about 150 years there are no examples of newly errected early christian gateways known. During the 8th century several gateways were restored or extended in Rome. Again, these buildings can be identified as very influential examples to gateways that were newly errected in the carolingian empire. These 8th/ 9th century gateways clearly follow the tradition of late antique propylea. The factors that lead to their construction are basically the same in both cases. Apart from that, their function covered a wider spectrum. Oratories were frequently incorporated. Compared to the architectural developement of the building type between the 4th and 6th century, a rather fast stylistic evolution of the 9th century gateways can be observed. Elements that were introduced during the carolingian epoque such as bell towers and chapels dedicated to the archangels were still used in some gateway- buildings that date after the end of the 9th century, but in most cases these features were incorporated in the main church buildings.