The Swedish STRIDA project on new psychoactive substances (NPS) monitored the occurrence and health hazards of novel recreational drugs in Sweden through evaluation of analytically confirmed adverse events presenting in emergency departments and intensive care units. During a ~6-year period from 2010 to early 2016, about 2,600 cases of suspected NPS intoxications were included in the project. About 75% of patients were men and the total age range was 8-71 (median 24) years and 57% were 25years or younger. A large number of NPS belonging to many different drug classes were identified in project samples of urine and blood (serum/plasma) submitted for free drug testing, including synthetic cannabinoid receptor agonists, stimulants, cathinones, hallucinogens, dissociative drugs, benzodiazepines, and opioids, and also in drug materials from the cases forwarded to the laboratory along with the biological samples. The STRIDA project has been shown to serve as an effective early warning system for NPS by collecting data on incidence, distribution, and adverse effects and has supported healthcare professionals in the knowledge and critical care of intoxications caused by a wide range of novel substances. The results of the STRIDA project have also illustrated how drug regulations can drive the NPS market.