Here, we review the current knowledge about the energetics of arginine insertion into the bilayer hydrocarbon core, and we discuss discrepancies between experimental and computational studies of the insertion process. While simulations suggest that it should be very costly to place arginine into the hydrocarbon core, experiments show that arginine is found there. Both types of studies suggest that arginine insertion into the bilayer involves substantial bilayer deformation, with multiple hydrogen bonds between the arginine guanidinium group and lipid polar groups. It is possible that the discrepancies concerning the insertion cost of arginine arise because simulations overestimate the cost associated with bilayer deformation and underestimate the ability of the bilayer to adapt to charged and polar groups. This is an active area of research, and there is no doubt that a consensus view of arginine in membranes will soon emerge.