ESDU 80027 presents data on the stress concentrations that occur around circular, elliptical, triangular, square or rectangular holes in flat plates under various combinations of loads in the plane of the plate. Data are also provided on the stress concentration when uniform section reinforcement is provided around the perimeter of the hole. For robust reinforcement around circular holes the stress concentrations at both the hole boundary and at the plate-to-reinforcement junction are provided. For lightweight reinforcement the critical concentration is that associated with the plate-to-reinforcement junction and this alone is provided. Data on the approximate equivalent symmetric area of unsymmetric reinforcement are provided together with notes and examples on their application in assessing the stress concentration in practical structures.