The indications of several well integrity failures on the Norwegian Continental Shelf (NCS) was the motivation for a study to investigate the possible involved mechanism of well integrity issues on the NCS. The study will include water injectors, gas injectors and CO2 injectors. This paper describes a number of technical well integrity issues, identifying critical elements such as design failures, corrosion problems, tubing leakage, operational factors and degradation of barrier elements like cement problems, casing issues and elastomeres failures in injection wells. The study includes a selection of new and old injection wells from different facilities and operating companies at the NCS. The paper will also present some production or injection wells in depleted oil and gas fields that are reused as injection wells. Well integrity and control of the barrier status is considered as an important HSE factor that limits integrity incidents, leaks and well control situations. Knowledge of the well status enables the companies to take the right actions in a proactive manner and thereby prevent potential losses and expenses and to ensure "healthy" & safe wells. Introduction Several well integrity failures in injection wells were reported to the Petroleum Safety Authority (PSA) in the "pilot well integrity survey" in 2006 referring to SPE 112535. The result of the referenced survey was the motivation for a study in 2008 to investigate the possible mechanisms of well integrity challenges on the NCS specifically related to injection wells. The data input in this study is based on format of the questionnaire for 2008 injection well study as referenced in appendix A. This study representing six operators includes water injectors, gas injectors and water alternating gas wells (WAG). Challenges regarding connections and CO2 injection are identified.