The subject of sampling practices was covered in all three previous editions of ASTM Special Technical Publication, ASTM STP 169, ASTM STP 169A, and ASTM STP 169B. The chapter in ASTM STP 169 was authored by C. E. Proudley. The chapter in STP 169A and 169B was authored by E. A. Abdun-Nur. Ed had planned to write the chapter for the current edition, but passed away shortly before the effort was initiated. The current chapter is largely Ed's work from the ASTM STP 169B, with references updated, and some additional information added on selected topics.