The barreling of cylindrical specimens during upsetting is a common example of free deformation. However, there is no analytical solution to predict the extent of barreling and even experimental work is scarce. In this study tests were conducted on 7075–0 aluminum with specimens of three height-to-diameter ratios. Some specimens were upset dry, others were lubricated. A suitable parameter was chosen to characterize the extent of barreling. The influence of various process variables on this parameter was studied. A simple analysis is given to relate this parameter to other geometrical factors. The possibility of analytical prediction of barreling is considered, but appears to be as yet remote.