Sample collection is the first step in petroleum, petroleum product, liquid fuel, and lubricant testing. This chapter discusses universal sampling considerations: sample heterogeneity, the respective roles of representative and nonrepresentative, diagnostic samples; the collection of replicate samples, sample chain of custody and handling; and sample container selection. The significance of each ASTM standard pertaining to petroleum and petroleum products—including alternative (nonpetroleum) fuel and lubricant products, such as vegetable oils, fatty acid methyl esters, alcohols, and so on—is then reviewed. The chapter includes a glossary compiled from all of the standards reviewed in the section “Sampling Practices.”