Produced water is routinely re-injected into many producing or disposal formations as a portion of ongoing operations. The inherent success of these operations is conditional on the ability to successfully inject the required volume of water in an economic fashion below the fracture gradient pressure of the formation under consideration. Many issues affect the success of a potential injection project, including well placement, geometry. and inherent formation quality and relative permeability characteristics. In addition to these factors, poor injection or disposal water quality can compromise the effective injectivity of even high duality sandstone or car Donate formations, resulting in economic failures and the need for costly workovers and recompletions on a regular basis to facilitate injection operations. This paper reviews the state of the art in diagnosing and evaluating injection water quality. and determining the effect of various potential contaminants such as suspended solids, corrosion products, skin/carryover oil and crease, scales, precipitates, emulsions; oil wet hydrocarbon agglomerates, and numerous other phenomena that can result in the degradation of injectivity. Screening criteria are presented, which review the process of analyzing the quality of a given injection or disposal formation, and the associated injection and disposal water. Suggestions for improving water quality, when required, are provided.