Screw-Piles and Helical Anchors have been in use throughout the world to support a variety of structures for the past 180 years and have seen a dramatic increase in use during the past 20 years. One of the important issues that must be considered in design is the degree of disturbance to the soil during installation. This may be especially important for tension applications in saturated fine-grained soils where the disturbance from installation may produce a reduction of the undrained shear strength and in structured soils where the installation produces a breakdown in the natural soil structure. In tension, the soil engaged in developing load capacity has unavoidably experienced the passing of the helical plates whereas in compression the soil beneath the lead plate is undisturbed. In order to evaluate the level of disturbance produced in different soils during installation, single-helix and multi-helix anchors were installed at several sites in the US and Brazil. Load tests were conducted in compression and tension to evaluate the difference in load behavior. The results show that even with perfect installation practice the soil is disturbed to some degree as a result of rotation of the helices during installation. The disturbance increases with additional helical plates which produces a reduction in individual plate load capacity. Using the results from compression and tension loading it is possible to define a capacity ratio which is in effect a disturbance factor for different soils. These results should help design engineers by recognizing the degree of installation disturbance that can occur and how it influences capacity.