Opiates are both therapeutical and illicit drugs used by the population. Notwithstanding the introduction of new psychoactive substances (NPS), in particular of new derivatives of fentanyl, opiates and heroin in particular, represents one of the most diffused illicit drug and still accounts for most of the seizures worldwide. The article presents an overview on opiates classification and their analgesic activity and pharmacology. Their potential of abuse in relation to general population and in case of tampering activities is described. Opiates are also strictly monitored in the workplace drug testing programs worldwide for the risks of accidents correlated to their use and dependence. Analytical methods for opiates detection in biological fluids are also discussed.