The effect of tapered ring reinforcements in reducing the stress concentrations around central holes in sheets under various biaxial stress fields in the elastic range was studied. The specimens were fabricated from plastic sheets as were the reinforcement rings. The rings were cemented symmetrically on each side of the sheet, and foil strain gages were mounted at various locations adjacent to the outer rim and at the inner rim of the reinforcements. The best tapered reinforcements gave maximum stress-concentration factors of 1.00, 1.10, 1.17, and 1.20 for 1:1, 1.5:1, 2:1, and 2.5:1 stress-field ratios, respectively. The initial effect of increasing the hub thickness or increasing the ring diameter is a sharp decrease in the stress-concentration factor at the inner rim; there is comparatively little effect on the stresses in the sheet. (Author).