The process of creating MR images frequently gives rise to artifacts in the final display. Many artifacts may be corrected or ameliorated through an understanding of their cause. This requires familiarity with scanner design; theory of operation; and image acquisition, generation, and display. Some artifacts are obvious, totally degrading the image; others are regional, leaving much of the scan undisturbed. In some cases, the degradation is permanent; in others, the data can be reprocessed or manipulated to yield artifact-free images. Some artifacts are overt and easily identified. Others, such as those caused by phase-shift or gradient-strength effects, are subtle and require careful observation for detection.