Tank inspections in the petroleum industry often include an evaluation of settlement effects. Tank failures and floating-roof problems have often been attributed to distortion of tanks due to settlement. In geotechnical practice evaluation of excessive settlement is done by referring to empirically derived limits that vary considerably.In this study the authors took settlement data from the literature and their own studies, and compared the results with limits commonly used in tank evaluations. On this basis tentative limit criteria are suggested that can be used in estimating the probability of the occurrence of tank problems.