Electronic grading for carcass yield is now a standard practice around the world, and the advantages of objective methodology in speed, fairness, and repeatability are widely appreciated. This chapter focuses on physical methods that make a direct contact with the carcass, although noninvasive techniques such as ultrasonics and nuclear magnetic resonance should not be forgotten, even though they have not yet been used to measure meat quality. To be of any practical value, an on-line method for meat quality must be fast enough to keep pace with commercial line speeds, cause only imperceptible damage to the carcass, and produce commercially useful information on meat quality. The optical measurement of meat quality involves a lot more than simply measuring color, although this is an important commercial property in its own right. Fiber optics are important because they provide the best means of making optical measurements within the muscles of an intact carcass before cutting.