Friction losses in post-tensioned concrete structures can account for more than 50% of the losses developed during prestressing operations. Accurate friction loss estimation is necessary for safe and economic design. Existing code equations and coefficients were developed in the 1950’s and first introduced in the ACI 318 guidelines in 1963, and no significant changes have been made since. Further, these equations were derived based on small-angle assumptions and do not consider effects related to strand interaction for multi-strand post-tensioning applications. The use of these equations in large-angle post-tensioning applications, such as hoop post-tensioning in cylindrical structures, may lead to unrealistic estimations of friction losses. In this paper, friction loss measurements were compared with estimated losses computed on the basis of current theory. Three 90-degree wall specimens were fabricated, each comprised of four evenly-spaced ducts that contained multiple strands. To evaluate friction losses, both live-end and dead-end loads were measured over the course of the stressing operations. Anticipated friction losses were on the order of about 33%; however, the measured losses were found to range from 40 to 60%. The large-angle configuration and strand-interaction within the ducts were identified as probable causes for the larger-than-anticipated friction loss results obtained.