Launch-vehicle shell structures, which can be comprised of both cylindrical and conical sections, are known to be susceptible to buckling due to their large radius-to-thickness ratios. The advancements in composite manufacturing and numerical methods have enabled designers to consider more nontraditional shapes, such as connecting the conical and cylindrical sections with a toroidal transition to create a single-piece conical-cylindrical shell. This single-piece construction eliminates the need for a heavy interface ring between sections and has the potential to save mass. To better understand the buckling behavior, a composite conical-cylindrical shell was designed, fabricated, and tested. Prior to test, a finite element model that included thickness variations and radial imperfections was created. The test article buckled elastically at 251.8 kN, approximately 8.8% higher than the predicted buckling load of 231.4 kN Continued research in conical-cylindrical structures has the potential to expand the design space for launch-vehicle structures and lead to improved designs and reduced weight.@en