This paper presents a theoretical and experimental investigation of the effect of various reinforcements on the stresses and displacements near a small circular hole in a plane sheet under load in its plane. The first part of the paper gives a plane-stress analysis for a reinforcement of variable thickness when the load is a uniform tension in all directions. It is found that a reinforcement which crowds most of the material close to the edge of the hole is most effective in reducing the stress concentration at the hole. The next part presents the principal results of earlier plane-stress analyses for reinforcement by a “doubler plate” when the load is tension in one direction only. The last part describes tests in the elastic range of riveted doubler-plate reinforcements of several sizes and with several rivet arrangements. Details of a test to failure of one reinforcement riveted to one side of the sheet only are given. The tests indicate that the plane-stress theory gives a good estimate of the state of stress outside the reinforcement, and that it may be used for computing median-surface stresses and average elongations of the hole in the specimen, provided that the reinforcement is attached to the sheet by more than one row of rivets.