New psychoactive substances are of continuously increasing interest. The continuous structural modifications for circumventing existing legislation pose a major problem for legislation and for forensic as well as clinical toxicology. Even after a legislative act came into force in November 2016 (New Psychoactive Substances Act, NpSG) that considers substances with defined structural features instead of individual substance regulations, substances have been developed that circumvent the legal stipulations. Above all, the supposedly legal alternatives with easy access pose a serious hazard to human health for users. In addition to the uncertainty about dosage, (qualitative and quantitative) composition of the consumed preparations and the associated risk for overdosing, the (side) effects are not or only insufficiently known for the majority of these substances. Health consequences can be severe and directly or indirectly lead to death.