The Expert Group reviewed current procedures in their countries regarding clandestine laboratory investigations. Experts from Austria, Canada, Germany, Hong Kong, Japan, the Republic of Korea, Thailand, the United Kingdom, and the United States gave detailed presentations on methods used in the clandestine production and investigation of priority drugs, namely, heroin, cocaine, PCP, amphetamines, methaqualone, and LSD. Presentations focused on the simplicity of extraction processes and chemical reaction schemes. The Expert Group considered the complementary roles of forensic chemists and law enforcement officers before, during, and after clandestine laboratory investigations. The following activities involved in such investigations were identified: planning the raid, assessing the laboratory, and processing the laboratory. Recognizing the need for international exchanges of information on clandestine laboratory investigations, the Expert Group made 13 recommendations related to the identification of clandestine laboratories, the training of forensic chemists and law enforcement officers, the use of standardized reporting systems, and the analysis of drug trends and clandestine drug production and manufacturing.