THE MATERIAL PRESENTED IN THIS CHAPTER IS A revision and update of the chapter by the same author in the previous edition (169C). While a number of changes have been made in this chapter (including the significantly expanded discussion of unconfined freeze-thaw testing), a great deal of the material continues to be based on the work of the chapter authors in the two editions of ASTM STP 169 previous to 169C. D. L. Bloem authored the section on soundness and deleterious substances in ASTM STP 169A and L. Dolar-Mantuani did the chapter of the same name in ASTM STP 169B. I am indebted to them for their work, most of which remains very valid today. Beginning with ASTM STP 169C, the subject of aggregate coatings was grouped with soundness and deleterious substances in this chapter. The discussion of coatings by M. A. Ozol in ASTM STP 169B was used as a basis for the inclusion of that subject. As with the previous edition, ASTM STP 169C, the chapter has been organized to concentrate on relevant ASTM standards and their use in dealing with these three aspects of aggregate quality.