Saudi Arabia is generally an arid country with a few exceptional sub-humidregions on the southwestern highlands. The southwestern highlands constitute one of the most fascinating and unusual ecoregions in the country with its natural forests. The main tree species prevailing in these forests is Juniperus procera Hochst. ex Endl. This species as well as other tree species are suffering an evident degradation due to different factors. Silvicultural practices are badly needed in order to rehabilitate the natural forests in Saudi Arabia. In this regard examining cross section characteristics and estimating the age of trees will offer the opportunity to obtain information about age, growth rates, and yield of these trees and to study the relation between tree growth and environmental factors. The results of the present investigation revealed that investigation of the disks from all sample trees showed that they had irregular shape and eccentric growth rings due to a lean form of the stem. Heartwood of Juniperus procera is purple red while sapwood is creamy white and they are clearly differentiated from each other with growth rings of both are distinct. Heartwood occupies the majority of the cross section surface at tree breast base (77.6%) while sapwood represented by only a narrow area (22%). So that the ratio of sapwood to heartwood accounted by about 28. Heart rot was seen in some of sampled trees. The estimate age of juniper trees in Taif ranged between 56 and 132 years with an average of 83 years while it was between 54 and 137 years with an average of 99 years in Baha region. Finally, the age of juniper trees in Asir region ranged between 52 and 142 years old with an average of 99.3 years.