This chapter provides a brief overview of illegal drugs as they are controlled internationally, the specific nature of some of these compounds and how they can be analysed. Generally speaking, controlled drug production and use tends to concentrate around four drugs or drug types: cannabis, opiates, cocaine and amphetamine‐type substances. This chapter discusses each of these together with a brief overview of the emerging new psychoactive substances (NPS). The choice of instrumental technique used in any analysis depends upon the motive behind the analysis and on the nature of the sample. Normal procedure when dealing with bulk samples is to perform presumptive color tests to identify the drug class, possibly followed by thin layer chromatography (TLC) to identify the specific member of the drug class. The analysis of drugs of abuse is a constant component of a forensic science laboratory and commonly encountered types of analysis preformed.