Drugs in bulk form or in blood or urine specimens are encountered in a wide variety of criminal cases, such as traffic accidents and fatalities, driving under the influence of alcohol or drugs, public intoxication, possession or sale of controlled substances, and illicit manufacture of controlled substances. The purpose of this chapter is to describe the various types of drugs commonly encountered by police and to examine some of the crime scene investigation issues with regard to this class of evidence. To simplify the topic, a distinction is made between bulk drugs (i.e., drugs in their usual solid or liquid form) and toxicological specimens (i.e., blood or urine samples that are to be tested to determine whether a drug is present in a person’s body). Some of the information is provided for general interest, as it is unlikely that the situation will be encountered by a general crime scene investigation unit. Investigations of suspicious deaths possibly involving drugs are often dealt with by special units attached to a pathology or coroner’s department, and breath testing for alcohol is likewise usually conducted by specially trained personnel.