Considerable information is available to date concerning the characteristics of the flow in the planetary boundary layer, which comprises roughly the lowest two thousand feet of the atmosphere. Unfortunately, in many instances, the results from different sources do not always agree. This is in part due to the extremely complex nature of the flow and as a result, some confusion exists as to the exact descriptions of the planetary layer. For this reason, a fairly extensive survey of the existing data has been carried out, and the results of this review are presented herein. The planetary layer is described in detail with respect to both mean velocity and turbulence, and the effect of thermal stability and surface conditions on these characteristics is discussed. Finally, a simplified analytical representation of the flow in the planetary layer is presented.