Abuse of designer drugs is widespread among young people, especially in the so-called “dance club scene” or “rave scene”, worldwide. Severe and even fatal poisonings have been attributed to the consumption of such drugs of abuse. However, in contrast to new medicaments, which are extensively studied in controlled clinical studies concerning metabolism, including cytochrome P450 isoenzyme differentiation, and further pharmacokinetics, designer drugs are consumed without any safety testing. This paper reviews the metabolism of new designer drugs of abuse that have emerged on the black market during the last years. Para-methoxyamphetamine (PMA), para-methoxymethamphetamine (PMMA) and 4-methylthioamphetamine (4-MTA), were taken into consideration as new “classical” amphetamine-derived designer drugs. Furthermore, N-benzylpiperazine (BZP), 1-(3, 4-methylenedioxybenzyl)piperazine (MDBP), 1-(3- trifluoromethylphenyl)piperazine (TFMPP), 1-(3-chlorophenyl)piperazine (mCPP) and 1-(4-methoxyphenyl)piperazine (MeOPP) were taken into consideration as derivatives of the class of piperazine-derived designer drugs, as well as αpyrrolidinopropiophenone (PPP), 4-methoxy-αpyrrolidinopropiophenone (MOPPP), 3, 4-methylenedioxy-αpyrrolidinopropiophenone (MDPPP), 4-methyl-αpyrrolidinopropiophenone (MPPP), and 4-methyl-αpyrrolidinoexanophenone (MPHP) as derivatives of the class of αpyrrolidinophenone-derived designer drugs. Papers describing identification of in vivo or in vitro human or animal metabolites and cytochrome P450 isoenzyme dependent metabolism have been considered and summarized.